Sealed and sealable lighting systems incorporating flexible light sheets and related methods

ABSTRACT

In accordance with certain embodiments, lighting systems include flexible light sheets and one or more sealed regions containing light-emitting elements, the sealed regions defined by seals between a top housing and a bottom housing and/or the light sheet. The top housing defines a plurality of shaped regions each associated with a light-emitting element and spaced apart from and not in contact with the light-emitting element with which it is associated.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/301,859, filed Jun. 11, 2014, which (i) claims the benefit of andpriority to U.S. Provisional Patent Application No. 61/834,183, filedJun. 12, 2013, the entire disclosure of which is hereby incorporatedherein by reference, and (ii) is a continuation-in-part of U.S. patentapplication Ser. No. 14/195,175, filed on Mar. 3, 2014, which is acontinuation of U.S. patent application Ser. No. 13/970,027, filed Aug.19, 2013, now issued as U.S. Pat. No. 8,704,448, which is acontinuation-in-part of U.S. patent application Ser. No. 13/799,807,filed Mar. 13, 2013, which claims the benefit of and priority to U.S.Provisional Patent Application No. 61/697,411, filed Sep. 6, 2012, theentire disclosure of each of which is hereby incorporated herein byreference.

FIELD OF THE INVENTION

In various embodiments, the present invention generally relates toelectronic devices, and more specifically to array-based electronicdevices.

BACKGROUND

Solid-state lighting is an attractive alternative to incandescent andfluorescent lighting systems for a wide range of lighting applicationsbecause of its relatively higher efficiency, robustness, and long life.However, conventional solid-state lighting systems featuringlight-emitting diodes (LEDs) have a number of limitations related tothermal management of heat generated by the LEDs and the need to controlthe distribution of light and ensure low glare.

In many lighting applications it is desirable to have lighting systemsor luminaires that are thin, low-volume, and lightweight in order tomeet certain aesthetic design requirements or so that the lightingsystem is unobtrusive. In other applications it is desirable to be ableto conform the illumination source to a curved surface. Current LEDsystems generally include LEDs that are operated at relatively highcurrent and thus very high brightness. High-current operation is oftenpreferred in order to reduce the LED count and thus reduce the overallcost of the lighting system. However, this results in the generation ofsignificant amounts of heat that must be extracted from the LED. Incontrast to incandescent lamps, which radiate heat into the environment,the heat from LEDs in large measure must be extracted by conduction,which generally requires relatively large amounts of material with ahigh thermal conductivity, such as metal core printed circuit boards(MCPCBs), heat sinks, and in some cases active (e.g., forced-air)cooling. Such thermal-management solutions typically are notsufficiently flexible to permit conforming to curved surfaces, and theytake up significantly more space than the LEDs themselves, resulting inincreased size and volume of LED-based lighting systems. These solutionsmay also increase system cost and potentially reduce reliability andoperational lifetime of the lighting system. The high junctiontemperatures associated with high-current operation also reduce LEDlifetime.

Furthermore, if not appropriately managed, high-brightness illuminationsources do not provide the desired light distribution pattern and mayproduce significant and unacceptable levels of glare. Such opticalchallenges have been addressed in a number of ways. For example, manylighting systems utilize a diffuser in front of the LEDs, but in orderto effectively reduce pixelization (i.e., the visualization of theindividual LEDs), the diffuser must have relatively low transmittance,which decreases efficiency. Some lighting systems utilize a large mixingvolume for the emitted light, which increases the size and cost of theillumination system, or utilize relatively sophisticated and costlyoptics to control the light-distribution pattern.

Thin, low-volume, and lightweight lighting elements are also beneficialfrom a building design and cost perspective. Virtually all buildingsrequire unoccupied space to support heating, ventilation, and airconditioning (HVAC) systems, electrical and communications wiring,plumbing, and other facilities. From a cost perspective it is desirableto minimize this unoccupied space, which often results in these spacesbecoming very crowded and densely packed, which can lead to difficultiesin initial installation and subsequent repair and modification of thesystems within the space. In some construction processes, lighting isinstalled closer to the end of the project, in which case the unoccupiedspaces may already be substantially filled, resulting in significantinstallation difficulty. Lighting systems that require significantvolume in the unoccupied space may thus increase the building cost byrequiring additional unoccupied space, or pose installation challengesif sufficient space has not been allotted in advance.

Space constraints also apply in building renovation. In these cases thespacing between floors is generally fixed and cannot be changed. Inparticular, many older buildings were not designed to support therequired range of facilities in more modern buildings. More unoccupiedspace can sometimes be created, but typically at the expense of theoccupied space, for example by reducing the ceiling height.

In view of the foregoing, a need exists for systems and techniquesenabling the low-cost design and manufacture of compact, reliable,high-brightness lighting systems having low glare and the ability toproduce different light-distribution patterns.

SUMMARY

In accordance with certain embodiments of the present invention,lighting systems incorporate flexible light sheets having light-emittingelements (e.g., bare-die light-emitting diodes) thereon. Top and orbottom housings, either or both of which may be polymeric, are utilizedto seal at least portions of the light sheets and form sealed regionsthat may be water-resistant or waterproof. The housings may also beshaped to reflect, diffuse, and/or shape the light emitted by thelight-emitting elements. The housings may even define structuralfeatures such as protruding ribs for mechanical stability. While most,if not all, of the light-emitting elements of the light sheets arepreferably safely located within the sealed regions, the lightingsystems typically incorporate conductive couplings that extend out ofthe sealed regions (without disrupting the seal over the light-emittingelements) and enable the provision of power from an external powersource to the light-emitting elements. Lighting systems in accordancewith embodiments of the invention may thus be advantageously deployed inharsher and/or moist environments where exposure to dirt, dust,moisture, etc. is possible or frequent. The lighting systems may befabricated in bulk by, e.g., roll-to-roll processes and even separatedfrom larger “sheets” of the lighting device components, preferablywithout disrupting the seal on and/or around each individual lightingsystem (or “partial” lighting system). As used herein, a “sealed region”refers to a portion of a light sheet or lighting system having aperiphery at least partially defined by a seal between two housings, ahousing and the light sheet, and/or a housing, light sheet, and/oranother sealing material (e.g., a transparent material disposed betweenthe light sheet and a housing. A sealed region may also include aportion of a light sheet coated with a housing, i.e., the housing may bea coating or sealant material conformally or non-conformally coating(and thus directly contacting) the portion of the light sheet (and,e.g., light-emitting elements, conductive traces, etc. on the lightsheet) thereunder.

In an aspect, embodiments of the invention feature a lighting systemincluding or consisting essentially of a substantially planar flexiblesubstrate having a first surface and a second surface opposite the firstsurface, first and second spaced-apart power conductors disposed overthe first surface of the substrate, a plurality of light-emittingstrings forming a two-dimensional array over the first surface of thesubstrate, a plurality of conductive traces disposed over the firstsurface of the substrate, a polymeric top housing disposed over thefirst surface of the substrate, and one or more conductive couplings forsupplying power from an external power source to the light-emittingstrings. Each light-emitting string (i) includes or consists essentiallyof a plurality of interconnected light-emitting elements spaced alongthe light-emitting string, (ii) has a first end electrically coupled tothe first power conductor, and (iii) has a second end electricallycoupled to the second power conductor. The power conductors supply powerto each of the light-emitting strings. Each conductive traceelectrically interconnects two light-emitting elements, or electricallyconnects a light-emitting element to a power conductor. The top housingseals (e.g., gaplessly seals), within a sealed region between the tophousing and the substrate, the plurality of light-emitting strings, theplurality of control elements, the plurality of conductive traces, atleast a portion of the first power conductor, and at least a portion ofthe second power conductor. One or more of the conductive couplingsextend from within the sealed region to outside of the sealed region.

Embodiments of the invention may include one or more of the following inany of a variety of combinations. The sealed region may bewater-resistant or waterproof. The sealed region may include or consistessentially of multiple individually sealed “sub-regions” each at leastpartially sealed from the others. The lighting system may include aplurality of control elements each (i) electrically connected to atleast one light-emitting string and (ii) configured to utilize powersupplied from the power conductors to control the current to the atleast one light-emitting string to which it is electrically connected.One or more (or even all) of the control elements may be disposed withinthe sealed region. A plurality of additional conductive traces may bedisposed over the first surface of the substrate. Each additionalconductive trace may (i) electrically interconnect a light-emittingelement and a control element, or (ii) electrically connect a controlelement to a power conductor. The control elements and the additionalconductive traces may be disposed within the sealed region. The firstand second power conductors may be disposed entirely within the sealedregion. The first and second power conductors may extend along opposingedges of the first surface of the substrate. The first and second powerconductors may extend in a first direction, and at least a portion ofeach of the plurality of light-emitting strings may extend in a seconddirection not parallel to (e.g., perpendicular to) the first direction.The top housing may be disposed in contact with, in the sealed region,the plurality of light-emitting strings, the plurality of controlelements, the plurality of conductive traces, the at least a portion ofthe first power conductor, and/or the at least a portion of the secondpower conductor. The top housing may be spaced apart from thelight-emitting strings and at least some of the conductive traces in thesealed region.

The lighting system may include a power supply for powering thelight-emitting elements and that is electrically connected to the firstand second power conductors. The power supply may be disposed within oroutside of the sealed region. The power supply may include or consistessentially of a battery. The power supply may be configured to providea substantially constant voltage to the power conductors. At least oneconductive coupling may be a portion of the first power conductor and/ora portion of the second power conductor. At least one conductivecoupling may be a wire electrically connected to at least one of thefirst or second power conductors within the sealed region and extendingoutside of the sealed region. At least one conductive coupling mayinclude or consist essentially of a conductive element (e.g., a rivet,staple, or crimp-type connector) piercing through at least one of thetop housing or the substrate and making electrical contact to at leastone of the first or second power conductors. At least one conductivecoupling may include or consist essentially of an electrical connectorterminating outside of the sealed region and configured to receive acomplementary connector or wire electrically connected to the externalpower source.

The lighting system may include a polymeric bottom housing disposed overthe second surface of the substrate (i.e., with the substrate disposedbetween the top and bottom housings). At least a portion of the bottomhousing may contact the second surface of the substrate to form a secondsealed region disposed between the bottom housing and the second surfaceof the substrate. The second sealed region may include or consistessentially of multiple individually sealed “sub-regions” each at leastpartially sealed from the others. The sealed region and the secondsealed region may be water-resistant or waterproof. The bottom housingmay be spaced away from the second surface of the substrate in thesecond sealed region. The bottom housing may be in contact with thesecond surface of the substrate in at least a portion of the secondsealed region. The bottom housing may include or consist essentially ofpolyester, acrylic, polystyrene, polyethylene, polyimide, polyethylenenaphthalate, polyethylene terephthalate, polypropylene, polycarbonate,acrylonitrile butadiene styrene, polyurethane, silicone, and/orpolydimethylsiloxane.

At least a portion of the bottom housing may contact the top housing(instead of or in addition to contacting the substrate) to form a secondsealed region disposed between the bottom housing and the second surfaceof the substrate. The sealed region and the second sealed region may bewater-resistant or waterproof. The bottom housing may be spaced awayfrom the second surface of the substrate in the second sealed region.The bottom housing may be in contact with the second surface of thesubstrate in at least a portion of the second sealed region. At least aportion of the bottom housing may define a plurality of protruding ribs.The bottom housing may include or consist essentially of polyester,acrylic, polystyrene, polyethylene, polyimide, polyethylene naphthalate,polyethylene terephthalate, polypropylene, polycarbonate, acrylonitrilebutadiene styrene, polyurethane, silicone, and/or polydimethylsiloxane.

The lighting system may include (i) control circuitry configured tocontrol at least one emission characteristic of the light-emittingelements, and/or (ii) communication circuitry configured to transmitinformation to or from the lighting system. The at least one emissioncharacteristic may include or consist essentially of a correlated colortemperature (CCT), a color rendering index (CRI), R9, a luminous flux, alight-output power, a spectral power density, a radiant flux, alight-distribution pattern, and/or an angular color uniformity. Thelighting system may have an ingress protection rating of at least IP 65,as specified by International Protection Marking in InternationalElectrotechnical Commission (IEC) standard 60529. The plurality oflight-emitting strings may form a fixed pattern in the shape of one ormore symbols and/or letters. The weight per area of the lighting systemmay be less than 5 kg/m², less than 3 kg/m², or less than 1.5 kg/m². Thethickness of the lighting system (including the top housing and/or abottom housing) may be less than 25 mm, less than 15 mm, less than 10mm, or less than 5 mm. At least a portion of the top housing may beconfigured as a diffuser for a wavelength of light emitted by thelight-emitting elements. A transmittance of the top housing for awavelength of light emitted by the light-emitting elements may begreater than 90%. The light-emitting elements in each of thelight-emitting strings may be separated by a substantially constantpitch. The top housing may be spaced apart from the light-emittingelements by an amount ranging from the pitch between light-emittingelements to twice the pitch between light-emitting elements.

At least one light-emitting element may emit substantially white light.A correlated color temperature of the substantially white light may bein the range of 2000 K to 10,000 K. At least one light-emitting elementmay include or consist essentially of a bare-die light-emitting diode.At least one light-emitting element may include or consist essentiallyof a packaged light-emitting diode. In at least one light-emittingstring, each light-emitting element may be coupled to one or moreconductive traces via solder and/or an adhesive. Each light-emittingelement in one or more light-emitting strings may be coupled to one ormore conductive traces via an anisotropic conductive adhesive. Theconductive traces may include or consist essentially of copper, brass,aluminum, silver, and/or gold. The thickness of the conductive tracesmay be less than 50 μm, and the substrate may include or consistessentially of polyethylene terephthalate. The sealed region may includean inert gas therewithin. The sealed region may be at least partiallyfilled with a flexible transparent material (which may be separate anddiscrete from the top housing, bottom housing, and/or substrate) havinga transmittance of at least 90% to a wavelength of light emitted by thelight-emitting elements. The sealed region may be filled with thetransparent material (i.e., the transparent material may occupy anyspace between the light sheet and the top housing in the sealed region).The transparent material may include or consist essentially of silicone,polyurethane, and/or epoxy. A desiccant may be disposed in the sealedregion. At least a portion of the top housing may define a plurality ofprotruding ribs.

At least a portion of an interior surface of the top housing may have areflectance greater than 90% to a wavelength of light emitted by thelight-emitting elements, and/or at least a portion of the substrate mayhave a transmittance greater than 90% to a wavelength of light emittedby the light-emitting elements. A portion of the top housing may beshaped to reflect light emitted by the light-emitting elements towardthe substrate. The top housing may include or consist essentially of aplurality of shaped regions each associated with a light-emittingelement. Each shaped region may include or consist essentially of ahemisphere, a portion of a sphere, or a paraboloid. Each shaped regionmay include or consist essentially of a paraboloid, and thelight-emitting element associated therewith may be positioned at a focalpoint of the paraboloid. An optical element may be disposed between thelight-emitting elements and the top housing. A plurality of opticalelements may be disposed between the light-emitting elements and the tophousing, and each optical element may be associated with one or morelight-emitting elements. The top housing may define a plurality ofshaped regions, each shaped region may be associated with alight-emitting element and may form at least a portion of an opticalelement thereover, and the top housing may have a transmittance greaterthan 90% to a wavelength of light emitted by the light-emittingelements. The shaped regions may each include or consist essentially ofa hemisphere, a portion of a sphere, or a paraboloid. A flexibletransparent material having a transmittance of at least 90% to awavelength of light emitted by the light-emitting elements may bedisposed between the polymeric top housing and the light-emittingelements. The transparent material may include or consist essentially ofsilicone, polyurethane, and/or epoxy. The transparent material may havea refractive index of at least 1.4.

The lighting system may be separable, via a cut spanning the first andsecond power conductors and not crossing a light-emitting string, intotwo individually operable partial lighting systems. Each partiallighting system may include or consist essentially of (i) one or morelight-emitting strings, (ii) portions of the first and second powerconductors configured to supply power to and thereby illuminate the oneor more light-emitting strings of the partial lighting system, (iii) asealed region defined by a seal between a portion of the top housing andthe substrate, and (iv) extending from within the sealed region tooutside of the sealed region, one or more of the conductive couplings.One or more control elements may be disposed in each partial lightingsystem. Each control element may be (i) electrically connected to atleast one light-emitting string and (ii) configured to utilize powersupplied from the power conductors to control the current to the atleast one light-emitting string to which it is electrically connected.The lighting system may be flexible. The top housing may include orconsist essentially of polyester, acrylic, polystyrene, polyethylene,polyimide, polyethylene naphthalate, polyethylene terephthalate,polypropylene, polycarbonate, acrylonitrile butadiene styrene,polyurethane, silicone, and/or polydimethylsiloxane.

The top housing may include or consist essentially of a transparentflexible material. The transparent material may include or consistessentially of silicone, polyurethane, and/or epoxy. The top housing mayconformally coat at least a portion of the first surface of the lightsheet. At least one conductive coupling may be configured to convey acommunication or control signal to or from the light sheet. Thecommunication or control signal may include or consist essentially of alight-intensity level, a correlated color temperature (CCT), a colorrendering index (CRI), a luminous-intensity distribution, and/or anoperational state of the light sheet. One or more second conductivecouplings configured to convey a communication or control signal to orfrom the light sheet may extend from within the sealed region to outsideof the sealed region. The communication or control signal may include orconsist essentially of a light-intensity level, a correlated colortemperature (CCT), a color rendering index (CRI), a luminous-intensitydistribution, and/or an operational state of the light sheet.

In another aspect, embodiments of the invention feature a method formanufacturing a lighting system. A light sheet is provided. The lightsheet includes or consists essentially of a substantially planarflexible substrate having a first surface and a second surface oppositethe first surface, first and second spaced spaced-apart power conductorsdisposed over the first surface of the substrate, a plurality oflight-emitting elements disposed over the first surface of thesubstrate, and a plurality of conductive traces disposed over the firstsurface of the substrate and each (i) electrically interconnecting twolight-emitting elements, or (ii) electrically connecting alight-emitting element to a power conductor. The light-emitting elementsmay be interconnected (e.g., serially connected) in one or morelight-emitting strings. Optionally, a polymeric bottom housing isprovided below a bottom surface of the light sheet. A polymeric tophousing is provided above a top surface of the light sheet opposite thebottom surface of the light sheet. At least a portion of the top housingis sealed to the light sheet and/or the bottom housing to form one ormore sealed regions containing the light-emitting elements.

Embodiments of the invention may include one or more of the following inany of a variety of combinations. The bottom housing may be provided,the at least a portion of the top housing may be sealed to the lightsheet, and at least a portion of the bottom housing may be sealed to thelight sheet. At least a portion of the bottom housing may be sealed tothe light sheet to thereby form one or more second sealed regionsdisposed between the bottom of the light sheet and the bottom housing.At least a portion of the bottom housing may be sealed to the tophousing. One or more of the sealed regions may be filled with an inertgas. One or more of the sealed regions may be partially or substantiallyfilled with a flexible transparent material having a transmittance of atleast 90% to a wavelength of light emitted by the light-emittingelements. The lighting system may be separated into a plurality ofindividually operable partial lighting systems each including orconsisting essentially of (i) one or more light-emitting elements, (ii)portions of the first and second power conductors configured to supplypower to and thereby illuminate the one or more light-emitting elementsof the partial lighting system, and (iii) one or more of the sealedregions. The transparent material may maintain (e.g., form a portion of)the seal between the top housing and the light sheet and/or the bottomhousing in the one or more sealed regions notwithstanding theseparation.

One or more conductive couplings for (i) supplying power from anexternal power source to one or more light-emitting elements and/or (ii)conveying a communication or control signal to or from the light sheetmay be provided. Each conductive coupling may extend from within asealed region to outside of the sealed region. The communication orcontrol signal may include or consist essentially of a light-intensitylevel, a correlated color temperature, a color rendering index, aluminous-intensity distribution, and/or an operational state of thelight sheet. The lighting system may be separated into a plurality ofindividually operable partial lighting systems each including orconsisting essentially of (i) one or more light-emitting elements, (ii)portions of the first and second power conductors configured to supplypower to and thereby illuminate the one or more light-emitting elementsof the partial lighting system, (iii) one or more of the sealed regions,and (iv) one or more of the conductive couplings. At least oneconductive coupling may be provided before the one or more sealedregions are formed. At least one conductive coupling may be providedafter the one or more sealed regions are formed.

The lighting system may be separated into a plurality of individuallyoperable partial lighting systems each including or consistingessentially of (i) one or more light-emitting elements, (ii) portions ofthe first and second power conductors configured to supply power to andthereby illuminate the one or more light-emitting elements of thepartial lighting system, and (iii) one or more of the sealed regions.The light-emitting elements may be interconnected to form a plurality oflight-emitting strings. Each light-emitting string (i) may comprise aplurality of interconnected light-emitting elements spaced along thelight-emitting string, (ii) may have a first end electrically coupled tothe first power conductor, and (iii) may have a second end electricallycoupled to the second power conductor. The power conductors may supplypower to each of the light-emitting strings. The light sheet may includethereon one or more control elements each (i) electrically connected toa different light-emitting string and (ii) configured to utilize powersupplied from the power conductors to provide a substantially constantcurrent to the light-emitting string to which it is electricallyconnected. Providing the top housing may include, before the one or moresealed regions are formed, shaping the top housing to define (i) one ormore protruding ribs and/or (ii) one or more optical elements. Providingthe top housing may include, before the one or more sealed regions areformed, coating at least a portion of the top housing with a coatinghaving a reflectance greater than 90% to a wavelength of light emittedby the light-emitting elements.

Each sealed region may be water-resistant or waterproof. Sealing atleast a portion of the top housing to the light sheet and/or the bottomhousing may include or consist essentially of heat welding,high-frequency welding, ultrasonic welding, laser welding, heat staking,gluing, and/or taping. Formation of the one or more sealed regions mayinclude or consist essentially of laminating the top housing to the topsurface of the light sheet. A transparent material having atransmittance of at least 90% to a wavelength of light emitted by thelight-emitting elements may be disposed over the first surface of thesubstrate. The transparent material may be provided before forming theone or more sealed regions. The transparent material may include orconsist essentially of silicone, polyurethane, and/or epoxy. Thetransparent material may be disposed over the substrate via dip coating,spray coating, brush coating, and/or printing. The transparent materialmay substantially conform to a non-planar topography of thelight-emitting elements thereunder. The top surface of the transparentmaterial may be planar notwithstanding a non-planar topography of thelight-emitting elements thereunder. The transparent material may also bedisposed over at least a portion of the second surface of the substrate.The transparent material may form a water-resistant or waterproofcoating. One or more sealed regions may each have an ingress protectionrating of at least IP 65, as specified by International ProtectionMarking in International Electrotechnical Commission (IEC) standard60529.

The light sheet may be provided on a first roll, the top housing may beprovided on a second roll, and the top housing may be sealed to thelight sheet. Sealing the top housing to the light sheet may include orconsist essentially of, in a roll-to-roll process, (a) feeding lightsheet from the first roll and top housing from the second roll to amating point, and at the mating point or thereafter, (b) sealing themated light sheet and top housing. The lighting system may be separatedinto a plurality of individually operable partial lighting systems eachincluding or consisting essentially of (i) one or more light-emittingelements, (ii) portions of the first and second power conductorsconfigured to supply power to and thereby illuminate the one or morelight-emitting elements of the partial lighting system, and (iii) one ormore of the sealed regions. One or more conductive couplings each (i)supplying power from an external power source to one or morelight-emitting elements and/or (ii) conveying a communication or controlsignal to or from the light sheet may be provided. Each conductivecoupling may extend from within a sealed region to outside of the sealedregion. At least one conductive coupling may be provided before the oneor more sealed regions are formed. At least one conductive coupling maybe provided after the one or more sealed regions are formed. Eachpartial lighting system may include one or more of the conductivecouplings. The communication or control signal may include or consistessentially of a light-intensity level, a correlated color temperature,a color rendering index, a luminous-intensity distribution, or anoperational state of the light sheet.

The light sheet may be provided on a first roll, the top housing may beprovided on a second roll, the bottom housing may be provided on a thirdroll, and sealing the top housing to the light sheet and/or the bottomhousing may include or consist essentially of, in a roll-to-rollprocess, (a) feeding light sheet from the first roll, top housing fromthe second roll, and bottom housing from the third roll to a matingpoint, and at the mating point or thereafter, (b) sealing the tophousing to at least one of the light sheet or the bottom housing. Thelighting system may be separated into a plurality of individuallyoperable partial lighting systems each including or consistingessentially of (i) one or more light-emitting elements, (ii) portions ofthe first and second power conductors configured to supply power to andthereby illuminate the one or more light-emitting elements of thepartial lighting system, and (iii) one or more of the sealed regions.One or more conductive couplings each (i) supplying power from anexternal power source to one or more light-emitting elements and/or (ii)conveying a communication or control signal to or from the light sheetmay be provided. Each conductive coupling may extend from within asealed region to outside of the sealed region. At least one conductivecoupling may be provided before the one or more sealed regions areformed. At least one conductive coupling may be provided after the oneor more sealed regions are formed. Each partial lighting system mayinclude one or more of the conductive couplings. The communication orcontrol signal may include or consist essentially of a light-intensitylevel, a correlated color temperature, a color rendering index, aluminous-intensity distribution, or an operational state of the lightsheet.

These and other objects, along with advantages and features of theinvention, will become more apparent through reference to the followingdescription, the accompanying drawings, and the claims. Furthermore, itis to be understood that the features of the various embodimentsdescribed herein are not mutually exclusive and can exist in variouscombinations and permutations. Reference throughout this specificationto “one example,” “an example,” “one embodiment,” or “an embodiment”means that a particular feature, structure, or characteristic describedin connection with the example is included in at least one example ofthe present technology. Thus, the occurrences of the phrases “in oneexample,” “in an example,” “one embodiment,” or “an embodiment” invarious places throughout this specification are not necessarily allreferring to the same example. Furthermore, the particular features,structures, routines, steps, or characteristics may be combined in anysuitable manner in one or more examples of the technology. As usedherein, the terms “about,” “approximately,” and “substantially”mean±10%, and in some embodiments, ±5%. The term “consists essentiallyof” means excluding other materials that contribute to function, unlessotherwise defined herein. Nonetheless, such other materials may bepresent, collectively or individually, in trace amounts.

Herein, two components such as light-emitting elements and/or opticalelements being “aligned” or “associated” with each other may refer tosuch components being mechanically and/or optically aligned. By“mechanically aligned” is meant coaxial or situated along a parallelaxis. By “optically aligned” is meant that at least some light (or otherelectromagnetic signal) emitted by or passing through one componentpasses through and/or is emitted by the other.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, like reference characters generally refer to the sameparts throughout the different views. Also, the drawings are notnecessarily to scale, emphasis instead generally being placed uponillustrating the principles of the invention. In the followingdescription, various embodiments of the present invention are describedwith reference to the following drawings, in which:

FIG. 1A is a circuit diagram of a portion of a light sheet in accordancewith various embodiments of the invention;

FIGS. 1B and 1C are schematic plan views of light sheets in accordancewith various embodiments of the invention;

FIGS. 2A and 2B are schematic cross-sections of lighting devices inaccordance with various embodiments of the invention;

FIG. 2C is a schematic cross-section of a portion of a lighting devicein accordance with various embodiments of the invention;

FIGS. 2D-2F are schematic cross-sections of lighting devices inaccordance with various embodiments of the invention;

FIGS. 3A and 3B are a schematic cross-section (FIG. 3A) and a partialschematic plan view (FIG. 3B) of a lighting device in accordance withvarious embodiments of the invention;

FIGS. 3C-3E are schematic cross-sections of lighting devices inaccordance with various embodiments of the invention;

FIG. 4 is a flowchart of a method of fabrication of lighting devices inaccordance with various embodiments of the invention;

FIG. 5A is a schematic cross-section of a light sheet in accordance withvarious embodiments of the invention;

FIGS. 5B and 5C are schematic cross-sections of portions of alighting-device housing in two stages of manufacture in accordance withvarious embodiments of the invention;

FIGS. 5D-5F are schematic cross-sections of electrical connections tolight sheets in accordance with various embodiments of the invention;

FIG. 5G is a schematic cross-section of a peripheral portion of alighting device in accordance with various embodiments of the invention;

FIGS. 5H-5J are schematic cross-sections of electrical connections tolight sheets in accordance with various embodiments of the invention;

FIGS. 5K and 5L are schematic cross-sections of a lighting device duringtwo stages of manufacture in accordance with various embodiments of theinvention;

FIG. 6A is a schematic plan view of a sheet separable into multiplelighting devices in accordance with various embodiments of theinvention;

FIGS. 6B-6D are schematic cross-sections of sheets separable intomultiple lighting devices in accordance with various embodiments of theinvention;

FIGS. 7 and 8 are schematic diagrams of roll-to-roll processingapparatuses for the fabrication of lighting devices in accordance withvarious embodiments of the invention;

FIG. 9A is a schematic cross-section of a lighting device in accordancewith various embodiments of the invention;

FIGS. 9B and 9C are schematic plan views of sheets separable intomultiple lighting devices in accordance with various embodiments of theinvention;

FIG. 9D is a schematic cross-section of a portion of a lighting devicehaving a crimp-type or punch-type electrical connection in accordancewith various embodiments of the invention;

FIGS. 9E and 9F are schematic plan views of a sheet separable (FIG. 9E)and separated (FIG. 9F) into multiple lighting devices in accordancewith various embodiments of the invention;

FIGS. 10A and 10B are schematic cross-sections of a laminated lightingdevice during two stages of manufacture in accordance with variousembodiments of the invention;

FIG. 10C is a schematic cross-section of a laminated lighting device inaccordance with various embodiments of the invention;

FIG. 10D is a schematic diagram of a roll-to-roll processing apparatusfor the fabrication of laminated lighting devices in accordance withvarious embodiments of the invention;

FIG. 11A is a schematic diagram of a roll-to-roll processing apparatusfor the fabrication of coated lighting devices in accordance withvarious embodiments of the invention;

FIGS. 11B-11D are schematic cross-sections of coated lighting devices inaccordance with various embodiments of the invention; and

FIGS. 12A-12D are schematic diagrams of electrical connectivity betweencomponents of lighting systems in accordance with various embodiments ofthe invention.

DETAILED DESCRIPTION

Various embodiments of the present invention feature a thin light sheetthat does not require any additional heat sinking or thermal management.In some embodiments, the light sheet may also be flexible and may becurved or folded to achieve one or more specific characteristics orattributes, for example, to permit manufacture of a compact, foldablesystem and/or to achieve a specific light-distribution pattern. In someembodiments of the present invention, the light sheet typically includesor consists essentially of an array of light-emitting elements (LEEs)electrically coupled by conductive elements formed on a flexiblesubstrate, for example as described in U.S. patent application Ser. No.13/799,807, filed Mar. 13, 2013 (the '807 application), or U.S. patentapplication Ser. No. 13/970,027, filed Aug. 19, 2013 (the '027application), the entire disclosure of each of which is herein herebyincorporated by reference.

FIG. 1A depicts an exemplary circuit topology of one embodiment of alight sheet, in accordance with embodiments of the present invention,which features conductive elements 160, at least two power conductors120, 121, multiple LEEs 140, and control elements (CEs) 145. In someembodiments, LEEs 140 may be configured in a regular periodic array, forexample a substantially square or rectangular array, where LEEs 140 areseparated by pitch (or “spacing”) 123 in one direction (for example, avertical or intrastring direction) and by pitch 125 in a substantiallyorthogonal direction (for example, a horizontal or interstringdirection). In some embodiments, pitch 125 is the same as orsubstantially the same as pitch 123. While the geometrical layout andpitches 123, 125 are described in connection with the circuit schematicshown in FIG. 1A, such geometry, layout, and pitches are not limitationsof the present invention, and in other embodiments the physical layoutof the circuit elements may be different than the circuit topology shownin FIG. 1A. Additionally, other embodiments may have different circuittopologies, for example LEEs 140 may be electrically coupled inparallel, in a combination of series and parallel, or any otherarrangement. In some embodiments, more than one group of electricallyconnected LEEs 140 may be electrically coupled to one CE 145, whileother embodiments may not require any CEs 145. The specific circuittopology is not a limitation of the present invention.

FIG. 1A shows two power conductors 120, 121, which may be used toprovide power to strings 150 of LEEs 140. Each string 150 may includetwo or more electrically coupled LEEs 140. LEEs 140 in string 150 may beelectrically coupled in series, as shown in FIG. 1A; however, this isnot a limitation of the present invention, and in other embodimentsother examples of electrical coupling may be utilized, for exampleparallel connections or any combination of series and parallelconnections. FIG. 1A shows CE 145 connected in series with LEEs 140 ofstring 150; however, this is not a limitation of the present invention,and in other embodiments CE 145 may have different electrical couplingbetween power conductors 120, 121, or may be absent altogether. Forexample, in some embodiments CE 145 may be separately electricallycoupled to power conductors 120, 121 and to the LEE string 150, while inother embodiments each CE 145 may be electrically coupled to two or morestrings. The number of strings electrically coupled to each CE 145 isnot a limitation of the present invention. Combinations of structuresdescribed herein, as well as other electrical connections, all fallwithin the scope of the present invention. Power conductors 120, 121 maybe used to provide power to strings 150, for example AC power, DC power,or power modulated by any other means.

Referring to FIGS. 1B and 1C that depict schematics of exemplary lightsheets 110, a light sheet 110 may feature an array of LEEs 140 eachelectrically coupled between conductive traces 160, as well as powerconductors 120, 121 providing power to conductive traces 160 and CEs145, all of which are disposed over a substrate 165. As utilized herein,a “wiring board” refers to a substrate for LEEs with or withoutadditional elements such as conductive traces or CEs. A wiring board mayalso be referred to as a light sheet or a circuit board. FIG. 1B shows aportion of a light sheet 110. In the exemplary embodiment depicted inFIG. 1B, power conductors 120, 121 are spaced apart from each other andlight-emitting strings (or simply “strings”) 150 are connected inparallel across power conductors 120, 121. In some embodiments, forexample as shown in FIG. 1B, strings 150 do not cross (i.e., intersect)each other. In other words, power conductors 120, 121 are oriented inone direction and strings 150 are oriented such that they span powerconductors 120, 121 in a different direction. As shown in FIG. 1B,strings 150 are substantially perpendicular to power conductors 120,121. However, this is not a limitation of the present invention, and inother embodiments at least some segments (i.e., portions connecting twoor more LEEs 140), or even the entire strings 150, may define a line(not necessarily a straight line) that is not perpendicular to powerconductors 120, 121 yet is (at least for an entire string 150) notparallel to power conductors 120, 121. In other embodiments, strings 150may intersect, for example one string 150 splitting into two or morestrings 150, or two or more strings 150 joining to form a reduced numberof strings 150. In some embodiments, conductive elements 160 may crossover each other without being electrically coupled to each other (i.e.,they may be electrically insulated from each other), and in someembodiments strings 150 may cross over or under each other without beingelectrically coupled to each other. In some embodiments, all or aportion of one or more strings 150 may extend outside of the area boundby power conductors 120, 121. Various examples of string geometries andconformations utilized in embodiments of the present invention aredescribed in the '807 and '027 applications.

As shown in FIGS. 1B and 1C, LEEs 140 may be positioned across substrate165 in a regular periodic array, although this is not a limitation ofthe present invention, and in other embodiments LEEs 140 may occupy anypositions on light sheet 110. Power conductors 120, 121 provide power toeach LEE string, for example the string 150 encircled by the dashed linein FIG. 1B. Each LEE string 150 typically includes multiple conductivetraces 160 that interconnect multiple LEEs 140, as well as one or moreCEs 145, which in FIG. 1B is in series with LEEs 140. String 150 shownin FIG. 1B is a folded string, i.e., a string that has three segmentselectrically coupled in series but positioned as three adjacentsegments. A string segment is a portion of a string spanning all or aportion of the region between power conductors 120, 121 in FIG. 1B. Inlight sheet 110, some string segments may include LEEs 140 while othersdo not. However, in other embodiments the distribution and position ofLEEs 140 along conductive elements 160 and string segments may bedifferent. In some embodiments, a string 150 may be a straight string,i.e., a string with no folds, as shown in FIG. 1C. (For simplicity, theexample shown in FIG. 1C does not depict CEs 145.) One end of string 150is electrically coupled to power conductor 120, while the other end ofstring 150 is electrically coupled to power conductor 121. As will bediscussed, the number of segments in a string 150 is not a limitation ofthe present invention. Various examples of straight and folded stringsutilized in embodiments of the present invention are detailed in the'807 and '027 applications.

FIGS. 1A and 1B illustrate three aspects in accordance with embodimentsof the present invention. The first is the multiple strings 150 that arepowered by the set of power conductors 120, 121. The second is thepositional relationship between the locations of LEEs 140 and CE 145,which is disposed between the conductive traces 160 and between powerconductors 120,121, such that the pitch between LEEs 140 is notdisrupted by the placement or position of CE 145. The third is theinclusion of a CE 145 in each string of series-connected LEEs 140.Combinations of these three aspects enable light sheet 110 to beeconomically manufactured in very long lengths, for example in aroll-to-roll process, and cut to specified lengths, forming lightsheets, while maintaining the ability to tile, or place light sheetsadjacent to each other (e.g., in the length direction), with no orsubstantially no change in pitch between LEEs 140 or in the opticalcharacteristics across the joint between two adjacent light sheets, asdiscussed in more detail in the '807 and '027 applications.

In an exemplary embodiment, CE 145 is configured to maintain a constantor substantially constant current through LEEs 140 of string 150. Forexample, in some embodiments, a constant voltage may be applied to powerconductors 120, 121, which may, under certain circumstances may havesome variation, or the sum of the forward voltages of LEEs 140 indifferent strings may be somewhat different, for example as a result ofmanufacturing tolerances, or the component and/or operational values ofthe element(s) within CE 145 may vary, for example as a result ofmanufacturing tolerances or changes in operating temperature, and CE 145acts to maintain the current through LEEs 140 substantially constant inthe face of these variations. In other words, in some embodiments theinput to the light sheet is a constant voltage that is applied to powerconductors 120, 121, and CEs 145 convert the constant voltage to aconstant or substantially constant current through LEEs 140. The designof CE 145 may be varied to provide different levels of control orvariation of the current through LEEs 140. In some embodiments, CEs 145may control the current through LEEs 140 to be substantially constantwith a variation of less than about ±25%. In some embodiments, CEs 145may control the current through LEEs 140 to be substantially constantwith a variation of less than about ±15%. In some embodiments, CEs 145may control the current through LEEs 140 to be substantially constantwith a variation of less than about ±10%. In some embodiments, CEs 145may control the current through LEEs 140 to be substantially constantwith a variation of less than about ±5%.

In some embodiments, CEs 145 may, in response to a control signal, actto maintain a constant or substantially constant current through LEEs140 until instructed to change to a different constant or substantiallyconstant current, for example by an external control signal. In someembodiments, as detailed herein, all CEs 145 on a sheet may act inconcert, that is maintain or change the current through all associatedLEEs 140; however, this is not a limitation of the present invention,and in other embodiments one or more CEs 145 may be individuallyinstructed and/or energized.

In some embodiments LEEs 140 may include or consist essentially oflight-emitting diodes (LEDs) or lasers. In some embodiments, lightemitted from light sheet 110 is in the form of an array of bright spots,or light-emission points, resulting in a pixelated pattern. However,this is not a limitation of the present invention, and in otherembodiments light sheet 110 includes different types of light emitters,for example organic LEDs (OLEDs). In some embodiments, light sheet 110may emit light homogeneously or substantially homogeneously, for examplelight sheet 110 may include an array of LEEs 140 behind an optic ordiffuser that spreads the light from LEEs 140 homogeneously orsubstantially homogeneously. In some embodiments, light sheet 110 mayinclude one or more OLEDs emitting homogeneously or substantiallyhomogeneously over light sheet 110.

In the embodiment depicted in FIG. 1B, LEEs 140 are distributedsubstantially uniformly over light sheet 110; however, this is not alimitation of the present invention, and in other embodiments, LEEs 140may have a non-uniform distribution. As will be understood, thedistributions of LEE 140 on light sheet 110 shown in FIGS. 1B and 1C arenot limitations of the present invention, and other embodiments may haveother distributions of LEEs 140. In some embodiments, one or moreportions of light sheet 110 may be unpopulated with LEEs 140. In someembodiments, the distribution of LEEs 140 on light sheet 110 isspecifically chosen to achieve one or more characteristics, for exampleoptical, electrical, thermal or the like, as described herein. In someembodiments, the distribution of LEEs 140 on light sheet 110 may bechosen to create a certain decorative look.

In some embodiments, light sheet 110 may also be cut to length, asdiscussed in more detail in the '807 and '027 applications. For example,in some embodiments of the present invention light sheet 110 may be cutbetween strings 150.

In some embodiments, light sheet 110 does not require any additionalthermal management or heat-sinking, i.e., the heat generated by LEEs 140is at least partially accommodated by the structure of light sheet 110itself, for example substrate 165 and/or conductive elements 160 and/orpower conductors 120, 121.

In some embodiments of the present invention, substrate 165 issubstantially covered with an array of LEEs 140 interconnected byconductive elements 160; however, in some embodiments one or moreportions of substrate 165 may not be populated with LEEs 140.

In some embodiments, all LEEs 140 in the lighting system may be drivenat the same or substantially the same current; however, this is not alimitation of the present invention, and in other embodiments differentLEEs 140 or different groups of LEEs 140 may be driven at differentcurrents.

In some embodiments, all LEEs 140 in the lighting system may have thesame optical characteristics, for example luminous or radiant flux, CCT,CRI, R9, spectral power distribution, light distribution pattern,angular color uniformity, or the like; however, this is not a limitationof the present invention, and in other embodiments different LEEs 140 ordifferent groups of LEEs 140 may have different optical characteristics.

FIGS. 2A-2F depict exemplary lighting devices in accordance withembodiments of the present invention, although alternative devices orsystems with similar functionality are also within the scope of theinvention. FIG. 2A shows a cross-sectional view of a lighting device 200of the present invention. (Conductive traces 160 are not shown in FIGS.2A-2F for clarity.) Lighting device 200 as shown is designed to beinstalled into a ceiling grid system, for example a T-grid 290, as shownin FIG. 2A; however; this is not a limitation of the present invention;and in other embodiments other grid systems may be used. In otherembodiments, lighting device 200 may be mounted using other techniques,for example it may be surface mounted or suspended. Lighting device 200includes a top housing 210, a bottom housing 220, and light sheet 110that includes substrate 165 and LEEs 140, as detailed above. As usedherein, the term “housing” broadly connotes any containment structure ormedium for fully overlying a top or bottom surface of the light sheet110. A housing may be rigid or flexible, polymeric or other material(e.g., glass), and may interconnect with or be bondable to the lightsheet or to another housing over the opposite surface of the light sheetto form a seal, e.g., a water-tight or water-resistant seal, around atleast a portion of the light sheet. In some embodiments of the presentinvention, top housing 210 and bottom housing 220 are fabricated fromplastic, for example polyester, acrylic, polystyrene, polyethylene,polyimide, polyethylene naphthalate (PEN), polyethylene terephthalate(PET), polypropylene, polycarbonate, acrylonitrile butadiene styrene(ABS), or the like. In some embodiments of the present invention tophousing 210 and bottom housing 220 are fabricated by molding orthermoforming.

In some embodiments of the present invention, the materials ofconstruction, for example substrate 165, top housing 210 and/or bottomhousing 220, include or consist essentially of materials having lowflammability. One measure of flammability is defined by UnderwriterLaboratories (UL) standard 94. UL94 includes various rating levels, forexample UL94 V-1, UL94 V-2, UL94 V-0, UL94 V5B, UL94 V5A, and the like.In some embodiments of the present invention, the materials ofconstruction are chosen to provide a certain level of flame retardanceto the lighting system, for example, as measured by the UL94flammability standard. In some embodiments of the present invention, thelighting system, for example as shown in FIG. 2A, 2C-2F, 3A-3E, 6B-6Dand the like, the lighting system has a UL94 rating of at least UL94V-1, or at least UL94 V-0, or at least UL94 5B, or at least UL94 5A.

In preferable embodiments of the present invention, all or a portion ofbottom housing 220 is transparent to a wavelength of light emitted byLEEs 140, for example having a transmittance to a wavelength of lightemitted by LEEs 140 of at least 75%, or at least 85%, or at least 95%.In some embodiments of the present invention, all or a portion of bottomhousing 220 may include a diffuser, for example to diffuse or scatter awavelength of light emitted by LEEs 140.

In some embodiments of the present invention, all or a portion of tophousing 210 is transparent to a wavelength of light emitted by LEEs 140,for example having a transmittance to a wavelength of light emitted byLEEs 140 of at least 75%, or at least 85%, or at least 95%, while inother embodiments all or a portion of top housing 210 may be translucentor opaque to a wavelength of light emitted by LEEs 140. In someembodiments of the present invention, all or a portion of housing 210 oran inner surface 211 of top housing 210 may be reflective to awavelength of light emitted by LEEs 140, for example having areflectance to a wavelength of light emitted by LEEs 140 of at least75%, or at least 85%, or at least 95%.

In some embodiments, portions of top housing 210 and/or bottom housing220 may be ribbed (i.e., have protruding segments), e.g., have one ormore ribs 230 in FIG. 2A, or otherwise structured to provide rigidity tolighting device 200.

In some embodiments of the present invention, top housing 210 and bottomhousing 220 may be joined at the periphery of lighting device 200, forexample in the region identified as 240 in FIG. 2A. In some embodimentsof the present invention, top housing 210 and bottom housing 220 may bejoined by heat welding, high-frequency welding, ultrasonic welding,laser welding, adhesive, glue, tape, or the like. In some embodiments ofthe present invention, top housing 210 and/or bottom housing 220 may bejoined to light sheet 110 or to each other within the periphery oflighting device 200.

In some embodiments of the present invention, housings 210, 220 may beconfigured to protect light sheet 110, for example to provide mechanicalprotection, protection from dust, water, etc. One method for ratingdifferent levels of environmental protection is an IP rating asspecified by International Protection Marking in InternationalElectrotechnical Commission (IEC) standard 60529, providingclassification of degrees of protection provided by enclosures forelectrical equipment, the entirety of which is hereby incorporated byreference herein. In some embodiments of the present invention, lightingdevice 200 may have any IP rating, for example from IP00 to IP 69k, orany other IP rating. In some embodiments of the present invention,lighting device 200 has an IP 44 rating, or an IP65 rating or an IP66rating or an IP67 rating or an IP68 rating. In general for an IP XYrating, “X” indicates the level of protection for access to electricalparts and ingress to solid foreign objects, while “Y” indicates thelevel of protection for ingress of harmful water. For example, an IP44rating provides access and ingress protection for objects greater thanabout 1 mm and protection from water splashing on the system. In anotherexample, an IP66 rating provides a dust-tight enclosure and protectionfrom water jets incident on the system. Specific details of therequirements and test method are detailed within the IP specification.

In some embodiments of the present invention, the interior region formedby housings 210, 220 may additionally contain a desiccant to absorbexcess moisture and/or water vapor and prevent degradation or corrosionof light sheet 110 and associated components. In some embodiments of thepresent invention, the interior region formed by housings 210, 220 maybe purged with an inert gas, for example nitrogen or argon, prior tosealing to reduce the moisture and/or water vapor concentration andprevent degradation or corrosion of light sheet 110 and associatedcomponents.

In some embodiments of the present invention, the interior region formedby housings 210, 220 may be evacuated to a relatively low pressure, ormay be filled with air. In some embodiments of the present invention,all or portions of the interior region formed by housings 210, 220 maybe filled with a material that is transparent or substantiallytransparent to a wavelength of light emitted by LEEs 140. In oneembodiment of the present invention, the transparent material includesor consists essentially of silicone, polyurethane, epoxy, or othersuitable materials. Examples of such transparent materials includematerials from the ASP series of silicone phenyls manufactured by ShinEtsu, or the Sylgard series manufactured by Dow Corning. In someembodiments of the present invention, the transparent material mayreduce total-internal-reflection (TIR) losses of LEEs 140 and mayprovide enhanced optical coupling between LEEs 140 and bottom housing220. In some embodiments of the present invention, the transparentmaterial has an index of refraction greater than about 1.4, or greaterthan about 1.45.

In some embodiments of the present invention, a flexible membrane ordiaphragm may be disposed within a portion of a housing or substrate 165to accommodate expansion and contraction of the atmosphere within thesealed region that may occur during storage and/or operation, forexample as a result of changes in temperature or altitude. In someembodiments of the present invention, all or a portion of a housing orsubstrate 165 has sufficient flexibility to accommodate such expansionsand contractions of the atmosphere within the sealed region.

In some embodiments of the present invention, lighting device 200 mayadditionally include one or more optical elements to control one or moreoptical characteristics, for example luminous or radiant flux, CCT, CRI,R9, spectral power distribution, light-distribution pattern, angularcolor uniformity, or the like. In some embodiments, the optical elementsmay include an optic substrate 264 having multiple optical elements 260on one side of optic substrate 264 and a second side (or “face”) 267opposite the first side that is substantially flat and positioned incontact or spaced apart from LEEs 140, as shown in FIG. 2B; however,this is not a limitation of the present invention, and in otherembodiments rear face 267 may be shaped or patterned. For example, insome embodiments of the present invention, rear face 267 of opticsubstrate 264 may include indentations 261 into which fit one or moreLEEs 140, for example as shown in detail in FIG. 2C.

Optical elements 260 associated with optic substrate 264 may all be thesame or may be different from each other. Optical elements 260 mayinclude or consist essentially of, e.g., a refractive optic, adiffractive optic, a TIR optic, a Fresnel optic, or the like, orcombinations of different types of optical elements. Optical elements260 may be shaped or engineered to achieve a specific light-distributionpattern from the array of light emitters, phosphors and opticalelements.

Optic substrate 264 typically features an array of optical elements 260;in some embodiments, one optical element 260 is associated with each LEE140, while in other embodiments multiple LEEs 140 are associated withone optical element 260, or multiple optical elements 260 are associatedwith a single LEE 140, or no engineered optical element is associatedwith any LEEs 140, for example portions of optic substrate 264 thereovermay merely be flat or roughened surfaces. In one embodiment, the opticalelements 260 scatter, diffuse, and/or spread out light generated by LEEs140.

FIG. 2B shows the axis of each optical element 260 as substantiallyaligned with the center of an LEE 140; however, this is not a limitationof the present invention, and in other embodiments optical element 260may be shifted in one or more lateral directions with respect to an LEE140, as detailed in U.S. Pat. No. 8,746,923, filed Dec. 4, 2012, theentire disclosure of which is incorporated by reference. It should benoted that alignment, as used herein, may mean that the center of onestructure, for example an LEE 140, is aligned with the center of anotherstructure, for example an optical element 260; however, this is not alimitation of the present invention, and in other embodiments alignmentrefers to a specified relationship between the geometries of multiplestructures.

Optical substrate 264 may be substantially optically transparent ortranslucent. For example, optical substrate 264 may exhibit atransmittance or reflectance greater than about 70% for opticalwavelengths ranging between about 400 nm and about 700 nm. Opticalsubstrate 264 may include or consist essentially of a material that istransparent to a wavelength of light emitted by LEE 140, for examplehaving a transmittance greater than about 75%, or greater than about 85%or greater than about 95% to a wavelength of light emitted by LEE 140.Optical substrate 264 may be substantially flexible or rigid. Opticalelements 260 may be formed in or on optical substrate 264. For example,optical elements 260 may be formed by etching, polishing, grinding,machining, molding, embossing, extruding, casting, or the like. Themethod of formation of optical elements 260 is not a limitation ofembodiments of the present invention.

Optic substrate 264 may include or consist essentially of, for example,acrylic, polycarbonate, polyethylene naphthalate (PEN), polyethyleneterephthalate (PET), polycarbonate, polyethersulfone, polyester,polyimide, polyethylene, glass, or the like. In some embodiments, opticsubstrate 264 includes or consists essentially of multiple materialsand/or layers.

The structure of FIGS. 2A and 2B shows the rear face 267 of opticsubstrate 264 spaced apart from LEEs 140; however, this is not alimitation of the present invention, and in other embodiments rear face267 of optic substrate 264 may be in contact with or substantially incontact with LEEs 140. Space 263 (FIG. 2C) and space 265 (FIG. 2B)between LEEs 140 and optic substrate 264 may be evacuated to arelatively low pressure, or may be filled with air or may be filled orpartially filled with a material that is transparent or substantiallytransparent to a wavelength of light emitted by LEEs 140. In oneembodiment of the present invention, the transparent material includesor consists essentially of silicone, epoxy or other suitable materials.Examples of such transparent materials include materials from the ASPseries of silicone phenyls manufactured by Shin Etsu, or the Sylgardseries manufactured by Dow Corning. In some embodiments of the presentinvention, the transparent material may reduce TIR losses in LEEs 140and may provide enhanced optical coupling between LEEs 140 and opticsubstrate 264. In some embodiments of the present invention, thetransparent material has an index of refraction greater than about 1.4,or greater than about 1.45.

Substrate 165 may be affixed to optic substrate 264 by theaforementioned transparent material or a similar material and/or byother means, for example adhesive, glue, tape, mechanical fasteners, orthe like. In one embodiment of the present invention, double-sided tape,such as 3M 467MP, is used to affix substrate 165 to optic substrate 264.In one embodiment of the present invention, a liquid adhesive, such asDymax 3099, is used to affix substrate 165 to optic substrate 264.

In some embodiments of the present invention, lighting device 200 mayhave lateral dimensions to fit or drop into standard-dimension gridceilings. For example, in North America some grid ceilings have griddimensions of about 2 feet by about 2 feet, or about 2 feet by about 4feet. In some embodiments of the present invention, lighting device 200may have a height in the range of about 50 mm to about 150 mm. In someembodiments of the present invention, lighting device 100 may have arelatively light weight, for example when housings 210, 220 include orconsist essentially of ABS, lighting device 200 may have a weight perarea of less than about 5 kg/m², or less than about 3 kg/m² or less thanabout 1.5 kg/m². In some embodiments of the present invention, lightingdevice 200 having dimensions of about 60 cm by about 60 cm may weighless than about 1 kg, or less than about 0.7 kg. In some embodiments ofthe present invention, lighting device 200 having dimensions of about 60cm by about 120 cm may weigh less than about 2 kg, or less than about1.4 kg. It should be noted that the weights described herein do notinclude a driver that drives LEEs 140. In some embodiments of thepresent invention, lighting device 200 may have a thickness less thanabout 70 mm or less than about 50 mm or less than about 30 mm, or lessthan about 15 mm or less than about 10 mm, or less than about 5 mm, orless than about 3 mm.

Relatively lightweight lighting devices have several advantages. First,they reduce the weight load on the building, potentially permitting areduction in new construction costs. Second, they are easier to handleand install. In some embodiments of the present invention, a lightweightlighting device may be installed, either temporarily or permanently,using hook-and-loop fasteners, adhesive, tape, dry wall hangers, nails,screws, or the like. Third, shipping costs typically depend on size andweight. The reduced weight of lighting devices of embodiments of thepresent invention may thus reduce shipping costs. The relatively thinprofile of lighting devices of embodiments of the present inventionpermits increased shipping density, for example more lighting devicesper shipping box or pallet, also resulting in lower shipping and storagecosts. In some embodiments, lighting devices or ribbed lighting devicesof embodiments of the present invention may be designed to stackrelatively tightly, with little need for additional space or packingmaterial for protection.

In some embodiments, bottom housing 220 may be eliminated and itsfunction replaced by optic substrate 264, as shown in FIG. 2D. In someembodiments of the present invention, optical substrate 264 may beeliminated and its function replaced by a shaped bottom housing 220.FIG. 2E shows one example of an embodiment of the present invention inwhich bottom housing 220 is shaped to have optical element shells 280,which in some embodiments correspond functionally to optical elements260 in FIG. 2B. In this embodiment, region 281 between LEEs 140 andbottom housing 220 is preferably filled or substantially filled with amaterial transparent to a wavelength of light emitted by LEEs 140, asdescribed herein.

In some embodiments of the present invention bottom housing 220,including optical shell elements 280, may be manufactured using athermoforming operation. Thermoforming or similar techniques permitrapid, low cost, accurate formation of shaped plastic components,resulting in a relatively low cost for lighting devices such as lightingdevice 200.

In some embodiments of the present invention, the thickness of tophousing 210 may be in the range of about 0.1 mm to about 5 mm, or in therange of about 0.3 mm to about 2.5 mm. In some embodiments of thepresent invention, the thickness of housings 210, 220 are substantiallythe same; however, in other embodiments, different portions of housings210, 220 may have different thicknesses. In one embodiment of thepresent invention, the thickness of bottom housing 220 in the regionbetween optical shell elements 280, identified as 282 in FIG. 2E, may bethinner than that of bottom housing 220 in shell elements 280,permitting flexing or bending of optic substrate 264 between opticalshell elements 280. In this embodiment, a lighting device may itselfhave a degree of flexibility, permitting curving or bending of theentire lighting device, as shown in FIG. 2F.

Lighting device 201, shown in FIG. 2F, includes substrate 165 on whichare formed LEEs 140 and that is mated to bottom housing 220. In thisembodiment of the present invention, top housing 210 is not utilized;however, this is not a limitation of the present invention, and in otherembodiments top housing 210 may be included in the structure of lightingdevice 201. While this example incorporates bottom housing 210 havingvariable thickness, this is not a limitation of the present invention,and in other embodiments bottom housing 220 may have a substantiallyuniform thickness. While the structure of FIG. 2F has been described asflexible, this is not a limitation of the present invention, and inother embodiments the structure of FIG. 2F may be rigid or substantiallyrigid.

In another embodiment of the present invention, a portion of the housingacts as a reflector for light emitted by LEEs 140. Lighting device 300of FIG. 3A includes LEEs 140 formed on substrate 165 which is mated to ahousing 310. As shown, housing 310 incorporates domes 320 or portions ofthe housing 310 have been shaped into domes 320. (Conductive traces 160are not shown in FIG. 3A for clarity.) In some embodiments of thepresent invention, the material of domes 320 and/or housing 310 arereflective to a wavelength of light emitted by LEEs 140, while in otherembodiments all or a portion of housing 310 is coated with one or morecoatings that are reflective of a wavelength of light emitted by LEEs140, for example having a reflectance greater than about 75%, or about85%, or about 95% to a wavelength of light emitted by LEEs 140. Forexample, in one embodiment of the present invention, the interiorsurface of dome 320 is coated with a reflective coating. In someembodiments of the present invention, the reflective coating includes orconsists essentially of aluminum, copper, silver, gold, chromium, or thelike. In some embodiments of the present invention, the reflectivecoating includes or consists essentially of a reflective metal coveredby one or more dielectric layers. In some embodiments of the presentinvention, the reflective coating is a dielectric mirror.

In these embodiments, substrate 165 is preferably transparent to awavelength of light emitted by LEEs 140, for example having atransmittance of at least 75% or at least 85%, or at least 95%. FIG. 3Bshows a plan view of a portion of lighting device 300 of FIG. 3A andshows conductive traces 160 that cover a portion of substrate 165 underdome 320. In some embodiments, conductive traces 160 are relativelythin, for example having a width 360 less than about 1 mm or less thanabout 0.5 mm or less than about 0.25 mm. In some embodiments, width 360is different (e.g., less) for portions of conductive traces 160 disposedunder dome 320, than it is outside of dome 320. In some embodiments, thearea of substrate 165 under dome 320 that is covered by conductivetraces 160 is less than 35% of total substrate 165 area under dome 320,or less than 25% of total substrate 165 area under dome 320, or lessthan 15% of total substrate 165 area under dome 320, or less than 5% oftotal substrate 165 area under dome 320, so as to minimize light loss aslight from LEE 140 is transmitted through substrate 165. In someembodiments, conductive traces 160 may include or consist essentially ofa transparent conductor, for example indium tin oxide (ITO), or othertransparent conductive oxides (TCOs).

In some embodiments of the present invention, the shape of domes 320 maybe engineered to produce different light-distribution patterns. Forexample, in one embodiment of the present invention, dome 320 has asubstantially paraboloid shape and LEE 140 is mounted substantially atthe focal point of the paraboloid, resulting in a relatively collimatedbeam 340 emitted from lighting device 300. In another embodiment of thepresent invention, dome 320 may have a hemispherical shape, or may be aportion of a hemisphere or paraboloid or may have any other shape. Insome embodiments, the region inside dome 320 may be evacuated, or filledwith air, or filled or partially filled with a material transparent to awavelength of light emitted by LEEs 140, as described herein.

In another embodiment of the present invention, the housing elementfacing LEEs 140 may be spaced apart from LEEs 140, for example as shownin FIGS. 3C and 3D. In some embodiments of the present invention, asshown in FIG. 3C, all or a portion of bottom housing 220 is transparentto a wavelength of light emitted by LEEs 140. In some embodiments of thepresent invention, all or a portion of bottom housing 220 is a diffuserand acts to diffuse or homogenize the light emitted by individual LEEs140, reducing or substantially eliminating pixelization and producing arelatively or substantially homogeneous plane of light, rather than avisible array of individual points of illumination.

In the lighting device of FIG. 3C, bottom housing component 220 isspaced apart from light sheet 110 by a spacing 370. In some embodiments,spacing 370 is about 1× to about 3× a spacing 125 between LEEs 140. Insome embodiments, spacing 370 is about 1.3× to about 2× the spacing 125.In some embodiments, a total thickness of 371 of the lighting device isin the range of about 5 mm to about 150 mm, or in the range of about 20mm to about 100 mm.

In some embodiments of the present invention, as shown in FIG. 3D, allor a portion of top housing 210 or a coating on the interior surface oftop housing 210 is reflective to a wavelength of light emitted by LEEs140, and all or a portion of substrate 165 is transparent to awavelength of light emitted by LEEs 140. Light 373 emitted by LEEs 140is directed towards and reflected from top housing 210 and exits thelighting device through light sheet 110. In some embodiments of thepresent invention, a bottom housing may be incorporated below substrate165 (i.e., opposite top housing 210).

In some embodiments of the present invention, all or a portion of bottomhousing 220 is a diffuser and acts to diffuse or homogenize the lightemitted by individual LEEs 140, reducing or substantially eliminatingpixelization and producing a relatively or substantially homogeneousplane of light. In some embodiments of the present invention, tophousing 210 or a coating on the interior of top housing 210 may be aspecular reflector, while in other embodiments it may be a diffusereflector. For example, in one embodiment of the present invention, tophousing 210 and/or a coating on all or a portion of the interior surfaceof top housing 210 may be a diffuse reflector and have a reflectancegreater than about 90%, and substrate 165 may be transparent to awavelength of light emitted by LEEs 140. In some embodiments, thespectral reflectance characteristics of top housing 210 or a coating onall or a portion of the interior surface of top housing 210 may beengineered to preferentially reflect or absorb one or more portions ofthe spectral power distribution from LEEs 140, resulting in the abilityto modify one or more spectral characteristics of the lighting device,for example CCT or CRI.

In some embodiments of the present invention, all or portions of thestructures of FIGS. 3C and 3D may be combined to produce lightingdevices similar to that shown in FIG. 3E. FIG. 3E shows a lightingdevice in accordance with embodiments of the present invention,including top housing 210 and bottom housing 220, both of which arespaced apart from light sheet 110. As discussed herein, all or a portionof top housing 210 may act as a specular or diffuse reflector, while allor a portion of bottom housing 220 may be transparent or a diffuser. Inthis lighting device, light emitted from LEEs 140 is directedsubstantially towards top housing 210, from which it is reflected andexits the lighting device after transmitting through light sheet 110 andbottom housing 220. As discussed herein, this structure reduces orsubstantially eliminates pixelization and results in a relatively orsubstantially homogeneous plane of light.

In some embodiments of the present invention, top housing 210 may permittransmission of a portion of light emitted by LEEs 140 to provideillumination in both upward and downward directions. For example, in oneembodiment of the present invention, the lighting device may provideboth direct and indirect illumination. In some embodiments of thepresent invention, top housing 210 may include or consist essentially ofone or more portions having a relatively high reflectance to awavelength of light emitted by LEEs 140 and one or more portions havinga relatively high transmittance to a wavelength of light emitted by LEEs140. In one embodiment of the present invention, top housing 210 mayhave substantially uniform optical characteristics, for example having atransmittance to a wavelength of light emitted by LEEs 140 in the rangeof about 20% to about 70% and a reflectance to a wavelength of lightemitted by LEEs 140 in the range of about 20% to about 70%, with theconstraint that the reflectance and transmittance may not together begreater than 100%.

The structures of FIGS. 2A-2F and 3A-3E may be manufactured in a varietyof ways. FIG. 4 shows a flow chart of a process 400 for forming thestructures of FIGS. 2A-2F and 3A-3E and similar structures. Process 400is shown having five steps; however, this is not a limitation of thepresent invention, and in other embodiments the invention has more orfewer steps and/or the steps may be performed in different order. Instep 410, a light sheet is provided. In step 420, housing material isprovided, e.g., as a single piece or multiple pieces of material. Instep 430, one or more pieces of housing (i.e., housing components) areformed from the housing material. In step 440, an electrical connectoris provided. In step 450, the housing component(s) and light sheet aremated to form the lighting device. In some embodiments of the presentinvention, the electrical connector is mated with the light sheet instep 450; however, this is not a limitation of the present invention,and in other embodiments the electrical connector may be mated with thelight sheet in a different step or in a separate step.

FIGS. 5A-5E depict one embodiment of process 400. In this embodiment, alight sheet 110 is provided in step 410, as shown in FIG. 5A. Themanufacture of the light sheet 110 includes provision of a substrate165, forming conductive traces 163 on the substrate 165, attaching andelectrically coupling LEEs 140 and optionally other components to theconductive traces 163 and the substrate 165. Additional details may befound herein and in the '807 and '027 applications. However, thespecific method of manufacture of light sheet 110 is not a limitation ofthe present invention, and in other embodiments other methods ofmanufacture of light sheet 110 may be utilized. For example, in someembodiments light sheet 110 may include or consist essentially of aninterconnected array of inorganic LEDs, while in other embodiments lightsheet 110 may include one or more organic light emitting diode (OLED)elements.

In step 420 the housing material is provided. Depending on the specificlighting device structure, this may be one piece of housing material ormultiple pieces of housing material. In some embodiments, the materialfor all housing components is the same, while in other embodimentsdifferent housing components may include or consist essentially ofdifferent materials. For example, for the device described in referenceto FIG. 2A, material for the housing components is provided, as shown inFIG. 5B. FIG. 5B shows two types of material 510, 520 that will be usedto manufacture top housing 210 and bottom housing 220 respectively. Inthis example material 520 is clear and has a transmittance to awavelength of light emitted by LEEs 140 greater than 95%, while material510 is white and has a reflectance to a wavelength of light emitted byLEEs 140 greater than 95%.

In step 430 the housing components are formed. In some embodiments ofthe present invention, forming may be cutting to a specific shape, whilein other embodiments this may include shaping the material, for exampleto have a specific three-dimensional shape. In other embodiments of thepresent invention, step 430 may include applying one or more coatings tothe materials provided in step 420. For example, for the devicedescribed in reference to FIG. 2A, material 510 is cut to size and ribsare formed therewithin by thermoforming to form top housing 210, whilematerial 520 is cut to size to form bottom housing 220, as shown in FIG.5C. The method of cutting, shaping, and/or coating of materials is not alimitation of the present invention.

In step 440 one or more electrical connectors to the light sheet areprovided. In some embodiments of the present invention, electricalconnection includes providing power to light sheet 110, for example topower conductors 120, 121, while in other embodiments communicationand/or control signals may also be required to be coupled to light sheet110. Electrical coupling to the conductive traces or power conductors onlight sheet 110 may be accomplished in a variety of ways. In someembodiments of the present invention, electrical coupling to theconductive traces may be accomplished by attaching wires to theappropriate conductive traces. In some embodiments, electrical couplingto the conductive traces may be accomplished by a pressure connection.

In some embodiments of the present invention, electrical coupling to theconductive traces may be accomplished by attaching one or more wires 530directly to a conductive element 540 (here conductive element refers toany conductive trace or power conductor on substrate 165), with solderor conductive adhesive or anisotropic conductive adhesive (ACA) 532, asshown in FIG. 5D. FIG. 5D shows wire 530 having optional insulation 534.In some embodiments of the present invention, electrical coupling to theconductive traces may be accomplished by attaching one or more wires 530to conductive element 540 by crimping, for example crimp 535 shown inFIG. 5E. Various crimp components may be used for this purpose, forexample Autosplice TC series or Nicomatic Crimplex series crimpconnectors; however, this is not a limitation of the present invention,and in other embodiments other crimp elements may be used.

In some embodiments of the present invention, electrical coupling to theconductive traces may be accomplished by attaching one or moreconnectors to the conductive traces, for example a Wago 2061 seriesconnector or a Molex Lite-Trap series connector; however, this is not alimitation of the present invention, and in other embodiments otherconnectors may be used. FIG. 5F shows an example of a connector 537electrically coupled to conductive element 540, for example using solderor conductive adhesive, and wire 530 inserted into connector 537. Insome embodiments, wire 530 may have a mating plug or component thatmates to connector 537 (not shown in FIG. 5F).

In some embodiments of the present invention, electrical connection toconductive element 540 may be formed within the housing of the lightingdevice and the wires attached to the light sheet may extend outside ofthe housing. In some embodiments of the present invention, a portion ofone or more conductive elements may extend beyond a portion of thehousing, permitting access and electrical coupling to the conductivetraces outside of the housing, for example as shown in FIG. 5G. FIG. 5Gshows a portion of substrate 165 and conductive element 540 extendingbeyond the edge of bottom housing 220, while being supported by tophousing 210; however, this is not a limitation of the present invention,and in other embodiments substrate 165 and conductive element 540 maynot be supported or fully supported beyond the edge of the housing. Insome embodiments of the present invention, one or more wires may beattached to the exposed portion of conductive element 540. In someembodiments, one or more connectors may be formed on the exposedportions of conductive element 540. In some embodiments of the presentinvention, a portion of conductive element 540 and a portion ofunderlying substrate 165 may be unsupported, i.e., not backed by aportion of bottom housing 210, and this may be mated with a connector,for example an edge connector or a zero-insertion-force-type connector.In the embodiment of the present invention shown in FIG. 5G, electricalconnection to conductive element 540 may be made using any of themethods described herein, for example soldering, conductive adhesive,crimping, ACA, or by other means.

In some embodiments of the present invention, housing 210, 220 may besealed over substrate 165 and conductive element 540. In someembodiments, wires attached to conductive traces 160 are placed betweentop housing 210 and bottom housing 220 before sealing, to provideelectrical access to light sheet 110. In some embodiments of the presentinvention, the seal of housing 210, 220 over substrate 165 andconductive element 540 or wire 530/534 may have an IP rating betweenIP00 and IP69k. In some embodiments of the present invention, the sealof housing 210, 220 over substrate 165 and conductive element 540 orwire 530/534 may have an IP 44 rating, an IP65 rating, an IP66 rating,an IP67 rating, or an IP 68 rating.

In some embodiments of the present invention, electrical connection toconductive element 540 may be made using a pressure connection. FIGS. 5Hand 5I show examples of pressure connections; however, other types ofpressure connections may be utilized. FIG. 5H shows clip 580 clampingwire 530 to conductive element 540. In FIG. 5I, wire 530 is replaced bya rectangular or square cross-section conductor 531, which is also heldin place with clip 580. In some embodiments of the present invention,clip 580 is spring-loaded, while in other embodiments clip 580 includesa means for applying pressure, for example a tightening screw or thelike. In some embodiments of the present invention, a conductive tape orconductive glue or ACA or anisotropic conductive film (ACF) 582 may beused to enhance electrical conductivity and robustness of the pressureconnection between wire 530 or 531 and conductive element 540, as shownin FIG. 5J. As discussed herein, such connections may be made inside thehousing or outside of the housing.

In step 450, the housing elements are mated with the light sheet 110 toform the lighting device. FIG. 5K shows top housing element 210, lightsheet 110, and bottom housing element 220 positioned before mating, andFIG. 5L shows the structure of FIG. 5K after mating. Note that in thisexample, light sheet 110 extends beyond the edge of top housing 210 andelectrical connection to conductive element 540 is made after step 450in region 590, as described herein.

In some embodiments of the present invention, top housing 210 and bottomhousing 220 may be joined by heat welding, high-frequency welding,ultrasonic welding, laser welding, adhesive, glue, tape, or the like. Insome embodiments of the present invention, light sheet 110 may beadhered to one or more portions of the housing, for example, top housingelement 210 or bottom housing element 220, before mating. In someembodiments of the present invention, light sheet 110 may be taped orglued to a portion of the housing before mating.

In some embodiments of the present invention, the interior region formedby housings 210, 220 may be purged and/or filled with an inert gas, forexample nitrogen or argon, prior to mating to reduce the moisture and/orwater vapor concentration and prevent degradation or corrosion of lightsheet 110 and associated components.

In some embodiments of the present invention the interior region formedby housings 210, 220 may be evacuated to a relatively low pressure, ormay be filled with air. In some embodiments of the present invention,all or portions of the interior region formed by housings 210, 220 maybe filled with a material that is transparent or substantiallytransparent to a wavelength of light emitted by LEEs 140, as describedherein. In some embodiments of the present invention, the transparentmaterial may also form the seal, for example between housing 210,housing 220, and/or light sheet 110.

In some embodiments of the present invention, lighting devices may bemanufactured in sheets or rolls and cut to length. FIG. 6A shows a planview and FIGS. 6B-6D show cross-sectional views of lighting devicesmanufactured according to various embodiments of the present invention.The structure of FIG. 6B is similar to that of FIG. 2F (without thecurvature), while the structure of FIG. 6C is similar to that of FIG.2A, and the structure of FIG. 6D is similar to that of FIG. 2E. Strings150 are shown in FIGS. 6A-6D without representation of the LEEs andinterconnects, for clarity, and as described herein, in some embodimentsof the present invention, light sheet 110 may be cut to length betweenstrings 150. FIG. 6A shows a plan view of a length of light sheet 110including multiple strings 150 and power conductors 120, 121 that may becut to length between strings 150, for example at a cut line 610. Cutline 610 is also shown for the structures of FIGS. 6B-6D. In oneembodiment of the present invention, the required components, forexample light sheet 110 and the required housing element or elements,are mated together before cutting. In some embodiments of the presentinvention, the interior region of the housing is filled with atransparent encapsulant or potting material, which itself provides aseal, for example an IP44, IP65, IP66, IP67, or IP68 rated seal, to thelight sheet and housing elements. With such a seal, sheets of lightingdevices may be cut to length while still maintaining their protectedquality or rating, for example their IP rating.

In some embodiments, lighting devices of the present invention may bemanufactured in a roll-to-roll process. FIG. 7A shows one embodiment ofthe present invention featuring a roll-to-roll process for manufactureof lighting devices; however, this is not a limitation of the presentinvention, and in other embodiments the process has more or fewer stepsand/or the steps may be performed in different order. The exemplarymanufacturing process shown in FIG. 7A begins with three material feedstreams, although this is not a limitation of the present invention, andin other embodiments fewer or more material feed streams may beutilized. A feed roll 710 supplies material 510 for top housing 210, afeed roll 720 supplies material 520 for bottom housing 220, and a feedroll 730 provides light sheet 110. Material 510 is optionally processedat a processing station 715, for example to cut, shape, or coat material510, as described herein, for example as described in relation to FIGS.5A-5L. Material 520 is optionally processed at a processing station 725,for example to cut, shape, or coat material 520, for example asdescribed in reference to FIGS. 5A-5L. Formed material 510′ and 520′ arebrought together with light sheet 110 at a mating point 740 and sealedat a sealing station 750, for example as described in reference to FIGS.5A-5L, and cut to length at a cutting station 755. Electrical contactsare formed at a wiring station 760. The output of sealing station 750 isan essentially a continuous lighting device 780, including light sheet110 in a housing. In the cutting station 755, the continuous lightingdevice 780 is cut into sections 785. In wiring station 760, electricalcontact is made to the light sheet, for example by a wire 790 beingelectrically coupled to the light sheet 110.

While the process described with respect to FIG. 7 shows completed lightsheet 110 as being supplied on a roll, this is not a limitation of thepresent invention, and in other embodiments lights sheet 110 may itselfbe manufactured in a roll-to-roll process that feeds into the system ofFIG. 7, for example as shown in FIG. 8. In FIG. 8, substrate 165 issupplied on a feed roll 810, and LEEs 140 are mated to substrate 165 ata bonding station 820. Light sheet 110 then feeds into the remainder ofthe process, as described with reference to FIG. 7. In some embodimentsof the present invention, conductive elements 540, for exampleconductive traces 160 and power conductors 120, 121, are pre-formed onsubstrate 165 and supplied on feed roll 810. In other embodiments of thepresent invention, conductive elements 540, for example conductivetraces 160 and power conductors 120, 121, are formed in-line onsubstrate 165, for example before bonding station 820. In someembodiments, conductive elements 540 may be formed using screenprinting, or lamination and etching or printing, for example ink jet,gravure printing or the like. The method of forming conductive elements540 on substrate 165 is not a limitation of the present invention.

While FIGS. 7 and 8 show the roll-to-roll process including asingulation or cutting step, for example at cutting station 755 in FIGS.7 and 8, this is not a limitation of the present invention, and in otherembodiments the singulation step may be removed from the roll-to-rollprocess, with the completed un-singulated structure being rolled upstored on a take-up roll (not shown in FIGS. 7 and 8).

In some embodiments, electrical contacts to light sheet 110 may beformed as described in reference to FIG. 5G, where a portion of aconductive element remains outside of the sealed housing. FIG. 9A showsone embodiment of the present invention in cross-section, lookingperpendicularly into cut line 610 of FIG. 6B, in which portions of powerconductors 120, 121 are not covered by top housing 210, permittingelectrical access to power conductors 120, 121 after the housing isformed, for example as described in reference to FIGS. 5H-5J and relatedtext. In other embodiments of the present invention, one or more wiresor connectors may be attached to the exposed portions of powerconductors 120, 121 before or after the housing is sealed. In someembodiments of the present invention, bottom housing 220 is optional.

FIG. 9B shows a plan view of the structure of FIG. 9A. The brackets onthe identifiers for substrate 165, bottom housing 220, power conductors120, 121 and top housing 210 indicate the width of these elements. Thecross-hatched portion of power conductors 120, 121, identified as 120′and 121′ in FIG. 9B, indicate the exposed portions of power conductors120, 121. In this example, portions of power conductors 120, 121 arefully exposed along the full length of the lighting device; however,this is not a limitation of the present invention, and in otherembodiments top housing may cover additional regions of power conductors120, 121 leaving periodically spaced exposed portions of powerconductors 120, 121 as shown in FIG. 9C. FIG. 9C shows a structuresimilar to that of FIG. 9B; however, in the structure of FIG. 9C onlyportions of power conductors 120, 121 are exposed periodically, notcontinuously as in the structure of FIG. 9B. The brackets on theidentifiers for bottom housing 220 and top housing 210 indicate thewidths of these elements. In FIG. 9C, substrate 165 is not shown forclarity. The exposed portions of power conductors 120, 121 areidentified as 120′ and 121′ in FIG. 9C.

In some embodiments of the present invention, electrical contacts may bemade by other techniques. For example, in some embodiments, a crimpconnection may be made through all or a portion of the housing and aportion of substrate 165 and a portion of a conductive element 540before or after the housing is sealed. In one embodiment of the presentinvention, the housing is sealed without exposure of any conductiveelements 540 and a crimp-type or punch-type connection 915 is madethrough the housing, as shown in FIG. 9D. The connection 915 may includeor consist essentially of a rivet or staple or other conductor piercingthrough the housing and electrically contacting and/or piercing powerconductor 120 and/or substrate 165.

In some embodiments of the present invention, electrical contacts may beformed before cutting or before sealing and cutting. Cutting is thenperformed in such a way that each cut light sheet section has theappropriate number and means of electrical connection, for example theappropriate number of wires or connectors. In some embodiments, the sealis performed over the wires.

FIG. 9E shows the structure of FIG. 6A at a later stage of manufacture.In FIG. 9E, multiple wires 910, 910′, 910″, and 911, 911′, 911″ havebeen attached to power conductors 120 and 121 respectively, at points920, 920′, 920″ and points 921, 921′, 921″, respectively. In thisexample, wire attachment points are spaced apart on a power conductor(for example power conductor 120, 121) by about four strings 150.

FIG. 9F shows the structure of FIG. 9E at a later stage of manufacture.In FIG. 9F, light sheet 110 has been mated and sealed into housing 930and cut to lengths corresponding to the spacing of the wire attachmentpoints 920 and 920′ and 921 and 921′, forming lighting devices 900 and900′, each of which has four strings 150 and wires 910 and 911 and wires910′ and 911′ electrically coupled to power conductors 120 and 121respectively. In FIG. 9F, the portions of the structure of FIG. 9Ecorresponding to wires 910″ and 911″ are not shown for clarity.

In some embodiments of the present invention, the electrical connectionhas the same protection rating, for example IP rating, as the housing,resulting in a system having the desired rating, for example IP 65, IP66, IP 67, or IP 68.

As discussed herein, other components may be formed on substrate 165 toprovide additional functionality to the lighting devices, for examplesensors, such as occupancy sensors, light sensors such as lightintensity sensors, humidity sensors, fire and/or smoke sensors,communication systems, or the like.

While the process described with respect to FIGS. 9E and 9F results inthe manufacture of multiple luminaires having substantially the samesize and properties, this is not a limitation of the present invention,and in other embodiments lighting devices having different lengths, ordifferent numbers of strings, may be manufactured on the same productionline by varying the spacing between wire attachment and cutting. In someembodiments of the manufacturing process of the present invention, thetype of LEEs 140 formed on substrate 165 may vary. For example, acontinuous process may be operated in which light sheet 110 having afirst type of LEE is manufactured for a given time or length and thenthe first type of LEE may be replaced with a second type of LEE, withoutstopping or significantly slowing down the manufacturing operation. Inone embodiment of the present invention, this may be accomplished in thesystem of FIG. 7 by replacing or splicing a second type of light sheetincluding the second type of LEE onto the material in feel roll 730 orby using a light sheet having different types of LEEs formed indifferent regions. In some embodiments, this may be done withoutstopping or significantly slowing down the roll-to-roll process. In someembodiments of the present invention, this may be accomplished in thesystem of FIG. 8 by replacing the first type of LEE with a second typeof LEE at bonding station 820 in FIG. 8. For example, different types ofLEEs may have a different CCT, CRI, luminous flux, R9, angular coloruniformity or the like.

In some embodiments of the present invention, CE 145 or one or morecomponents making up CE 145 may be changed in the manufacturing processwithout stopping or significantly slowing down the roll-to-roll process,in a similar fashion as that described herein for changing the type ofLEE. For example, feed roll 730 in FIG. 7 may include light sheet 110with different portions, each portion having a different CE 145 or oneor more different components making up CE 145 or a second light sheet110 having a different CE 145 or one or more different components makingup CE 145 may be spliced onto feed roll 730. In some embodiments of thepresent invention, CE 145 or the components making up CE 145 may beformed on substrate 165 in bonding station 820 of FIG. 8. In someembodiments of the present invention, the type of CE 145 or one or morecomponents of CE 145 making up CE 145 may be changed during themanufacturing process, without stopping or significantly slowing downthe roll-to-roll manufacturing process. In some embodiments of thepresent invention, the pattern of conductive elements on substrate 165may be varied during the manufacturing process, for example in thesystem of FIG. 8, substrate 165 is supplied to bonding station 820 andwithin bonding station 820, the conductive elements may be formed onsubstrate 165 as well as LEEs 140 and CEs 145.

Such embodiments of the invention result in the ability to manufacturelarge volumes of lighting devices in a roll-to-roll process with astandardized product, with a semi-custom product or with a fullycustomized product. For example, customization may include differentLEEs 140 having different properties, different conductive tracepatterns, different pitch or patterns between LEEs, different drivecurrents for LEEs 140, or different types of material for the housing.For example, housing elements 210, 220 may include or consistessentially of different materials, for example a transparent housingelement and a diffusing housing element, or a different thicknessmaterial for the housing. Customization may also include options fordifferent substrate materials, for example transparent or opaque to awavelength of light emitted by LEEs 140, or different thicknesssubstrate, different additional elements such as sensors, communicationdevices, or the like. In an automated system, in one embodiment of thepresent invention, the desired quantity and parts are programmed intothe system, which then manufactures, in a continuous process, a widerange of differentiated or customized lighting devices having differentelectrical, optical or physical characteristics.

In another embodiment of the present invention, lighting devices may bemanufactured entirely or in part by lamination. For example, the housingmay be fabricated by lamination, as when a top housing 210 is formedover LEEs 140 and an optional bottom housing 220 by lamination. In thelamination process, a layer is formed and adhered to light sheet 140over LEEs 140, providing for example mechanical protection and/orelectrical protection (covering conductive traces and other electricallyactive elements), water and/or moisture protection for example toachieve an IP rating, dust protection, and the like.

In some embodiments, the layer of film to be laminated is adhered to thelight sheet using a liquid adhesive that is applied to the light sheetor the film or both before mating, or a dry adhesive that is applied tothe film or light sheet or both before mating. In some embodiments,lamination may be performed on a sheet basis, while in other embodimentslamination may be performed using a roll-to-roll process.

FIG. 10A shows one embodiment of the present invention that utilizes apouch lamination process; however, other embodiments may have more orfewer steps and/or the steps may be performed in a different order.Light sheet 110 is inserted into an opening 1040 of a pouch 1030, whichincludes a top pouch layer 1010 and a bottom pouch layer 1020. Adhesiveis disposed on portions or all of the interior surface of pouch 1030.Pressure and/or heat is then applied to the structure of FIG. 10A,resulting in the laminated structure of FIG. 10B. In another embodimentof the present invention, only a top lamination layer, for example toppouch layer 1010, is used, and substrate 165 forms the back of thelaminated structure, as shown in FIG. 10C.

In some embodiments of the present invention, lamination is performed ina roll-to-roll process, for example as shown in FIG. 10D. FIG. 10D showsa feeder roll 1011 for top lamination film 1010, a feeder roll 1021 foroptional bottom lamination film 1020, a feeder roll 1015 for light sheet110, and a lamination stage 1040. Light sheet 110 is mated with toplamination film 1010 and optionally bottom lamination film 1020 atlamination stage 1040, producing the final structure 1050. In someembodiments of the present invention, laminated light sheet 1050 is cutinto sheets after lamination stage 1040, while in other embodimentslaminated light sheet 1050 is rolled up onto a take-up roll 1070. Insome embodiments of the present invention, lamination stage 1040 is acold lamination process, in which lamination occurs substantiallythrough the application of pressure. In some embodiments of the presentinvention, lamination stage 1040 is a hot lamination process, in whichlamination occurs through the application of both heat and pressure.Some embodiments of the present invention may utilize a lamination tape,which is laminated on light sheet 110 substantially through theapplication of pressure.

In some embodiments, the lamination film may include or consistessentially of a semicrystalline or amorphous material, e.g.,polyethylene naphthalate (PEN), polyethylene terephthalate (PET),polycarbonate, polyethersulfone, polyester, polyimide, polyethylene, orthe like. In some embodiments, the lamination film is the same materialas substrate 165, while in other embodiments the lamination film is adifferent material. In preferred embodiments of the present invention,the lamination film is transparent to a wavelength of light emitted byLEEs 140, for example having a transmittance greater than about 75% orgreater than about 85% or greater than about 95% to such light.

In some embodiments of the present invention, variations in theroll-to-roll lamination manufacturing process may be the same as orsimilar to those described herein with respect to other roll-to-rollmanufacturing processes, for example with reference to FIGS. 8 and 9. Insome embodiments of the present invention, methods of making electricalcontact to a laminated light sheet may be similar to or the same asdescribed herein with respect to other configurations of the presentinvention.

In some embodiments of the present invention, the housing may be formedvia a coating process. In some embodiments, a coating may be a conformalor substantially conformal coating, while in other embodiments thecoating may not be conformal. In some embodiments, a coating may includeor consist of one layer, while in other embodiments a coating mayinclude or consist essentially of more than one layer. In someembodiments of the present invention, a multi-layer coating may includeor consist essentially of multiple layers of the same material, while inother embodiments a multi-layer coating may include or consistessentially of different materials. In some embodiments of the presentinvention, multiple layers may be used to ensure integrity of thecoating material, for example to reduce the occurrence of or eliminatepinholes or other defects that may compromise the integrity of thecoating.

FIG. 11A shows one embodiment of the present invention that utilizes acoating process; however, other embodiments may have more or fewer stepsand/or the steps may be performed in a different order. FIG. 11A showsone embodiment of the present invention for manufacture of a coatedlight sheet; however, in other embodiments, the number of steps in theprocess may be greater or fewer and the steps may be performed in adifferent order. In the process of FIG. 11A, light sheet 110 is suppliedon a feed roll 1165. Light sheet 110 is passed through a coating bath1110 containing coating material 1120 (typically in liquid form),resulting in a coated material 1130 that is then cured at a curing stage1130, resulting in a coated light sheet 1140 that is stored on a take-uproll 1166. In some embodiments, coating stage 1130 includes or consistsessentially of a thermal cure; however, this is not a limitation of thepresent invention, and in other embodiments other curing methods may beused, for example UV cure, radiation cure, room temperature cure,moisture-induced curing, or the like. While FIG. 11A shows aroll-to-roll coating process, this is not a limitation of the presentinvention, and in other embodiments coating may be performed on asheet-by-sheet basis. While FIG. 11A shows a dip coating process, thisis not a limitation of the present invention, and in other embodimentsthe coating material may be applied by other techniques, for examplespraying, brushing, doctor blade, or printing (e.g., screen, gravure orother printing methods).

FIG. 11B shows an example of coated light sheet 1140 with a conformal orsubstantially conformal coating 1180, while FIG. 11C shows an example ofcoated light sheet 1140 with a non-conformal coating 1180. In someembodiments of the present invention, coating 1180 is applied to thefront side of light sheet 110 but not the opposite side of light sheet110, as shown in FIG. 11D.

In some embodiments of the present invention, variations in the coatingmanufacturing process may be the same as or similar to those describedherein with respect to other roll-to-roll manufacturing processes, forexample with reference to FIGS. 8 and 9. In some embodiments of thepresent invention, methods of making electrical contact to coated lightsheet may be the same as or similar to those described herein withrespect to other configurations of the present invention.

In some embodiments of the present invention, the housing or coating orlamination material is sealed to light sheet 110, for example to thesubstrate 165 between LEEs 140, such that cutting light sheet 110between LEEs 140 retains the integrity of the protection (i.e., does notexpose individual LEEs 140 to the outside ambient). For example, in someembodiments of the present invention, the completed structure, includingthe covering material, for example a housing, a coating, a lamination orthe like, may have an IP 44 rating or higher, for example IP65, IP 66,IP67, IP 68 or the like both before and after cutting of the structurebetween LEEs 140 to form two or more completed structures.

While lighting devices of the present invention have been described withreference to use in grid or T-grid ceiling systems, this is not alimitation of the present invention, and in other embodiments lightingdevices of the present invention may be mounted in other configurations,for example flush mounted to a surface such as a ceiling or a wall,suspended from one or more cables, mounted on a pole, or the like.

In some embodiments of the present invention, all or portions ofpolymeric bottom housing 220 and/or polymeric top housing 210 and/orsubstrate 165 may have decorations or designs attached to them orprinted on them. In some embodiments of the present invention, all orportions of polymeric bottom housing 220 and/or polymeric top housing210 and/or substrate 165 may be colored.

FIG. 12A shows one embodiment of the present invention that features alighting device 1210 and a driver or power supply 1220. Driver 1220 ispowered by, e.g., an AC mains 1230, for example having a voltage ofabout 120 VAC or a voltage of about 240 VAC or about 277 VAC; however,the value of the voltage and/or its time dependence (i.e., AC or DC oranother arbitrary waveform) are not limitations of the presentinvention. In some embodiments of the present invention, driver 1220 isa substantially constant voltage supply. In some embodiments of thepresent invention, the output of driver 1220 is pulse-width modulated toenable dimming of LEEs 140. In some embodiments, driver 1220 has a ULclass 2 rating, having a voltage output not exceeding 60 V. In someembodiments of the present invention, driver 1220 may include a batterybackup system, to provide power to lighting system 1210 in case of afailure of main power 1230.

In some embodiments of the present invention, driver 1220 is locatedoutside of lighting device 1210, where, for example, lighting device1210 is similar to the lighting devices shown in FIGS. 2A, 2B, 2E, 2F,or the like. In some embodiments, one driver 1220 may power one lightingdevice 1210, as shown in FIG. 12A, while in other embodiments one driver1220 may power more than one lighting device 1210, as shown in FIG. 12B.FIG. 12B shows one embodiment of the present invention that featuresthree lighting devices 1210, with two connected electrically in seriesand one connected electrically in parallel to the series-connectedlighting device 1210; however, this is not a limitation of the presentinvention, and in other embodiments all lighting devices may beconnected in series, or all lighting devices may be connected inparallel or they may be connected in any other configuration. While FIG.12B shows three lighting devices 1210, this is not a limitation of thepresent invention, and in other embodiments fewer or more lightingdevices 110 may be utilized. FIG. 12B shows three lighting devices 1210that are substantially the same; however, this is not a limitation ofthe present invention, and in other embodiments driver 1220 may providepower to different types of lighting devices 1210, for example havingdifferent sizes, different numbers of LEEs 140 or different spectral oroptical characteristics. In some embodiments, driver 1220 may beincorporated in the housing of the lighting device 1210, as shown inFIG. 12C.

In some embodiments, control and/or communication signals, either to orfrom the lighting system, or in two-way communication with the lightingsystem, may also be enabled in embodiments of the present invention. Forexample, such signals may include a dimming signal, signals providingsensor output (e.g., from a sensor such as a light sensor, occupancysensor or the like), connection to a lighting control system (e.g.,DALI, DMX or the like), or a facilities management system, a safetysystem, or the like. In some embodiments of the present invention, suchsensors may be incorporated within driver 1220, or within lightingdevice 1210 or on light sheet 110, while in other embodiments suchsensors may be incorporated externally to lighting device 1210 anddriver 1220.

In some embodiments of the present invention, such signals may providecontrol information to the lighting system, for example to energize it,to de-energize it, to change the light level (e.g., dimming), to changethe CCT, to change the spectral power density, to change the luminousintensity distribution or the like. In some embodiments of the presentinvention, such signals may provide information about the lightingsystem, for example a defect or failure in lighting device 1210 and/ordriver 1220, the temperature of lighting device 1210 and/or driver 1220,the location of lighting device 1210 and/or driver 1220, the opticalcharacteristics of lighting device 1210 or the like.

In some embodiments of the present invention, one or more control and/orcommunication signals may be transmitted to driver 1220, while in otherembodiments one or more control and/or communication signals may betransmitted to lighting device 1210, or in other embodiments one or morecontrol and/or communication signals 1240 may be transmitted to bothdriver 1220 and lighting device 1210, as shown in FIG. 12D. In someembodiments of the present invention, such control and/or communicationsignals may be transmitted to lighting device 1210 and/or driver 1220wirelessly, for example using light-based communication such asinfra-red (IR) or ultra-violet (UV) or visible light, radio-basedcommunication, for example WIFI, Bluetooth or the like. The methodand/or protocol of control and communication signal transmission todriver 1220 and/or lighting device 1210 is not a limitation of thepresent invention.

In some embodiments, warning or other annunciation signals may bedisplayed by lighting device 1210. In some embodiments of the presentinvention, light sheet 110 or portions of light sheet 110 or lightingdevice 1210 may be energized and de-energized to provide a blinkingindication. In some embodiments of the present invention, light sheet110 may be cut or formed into one or more shapes, symbols or letters, toprovide additional information or indications. For example light sheet110 may be shaped into an arrow, a stop sign, a cross, or other shapes.In some embodiments of the present invention, LEEs 140 on light sheet110 may be positioned to form one or more shapes, symbols or letters,for example an arrow, a “DO NOT ENTER” sign, a no smoking symbol, a noentry symbol, a symbol for fire, or the like.

As utilized herein, the term “light-emitting element” (LEE) refers toany device that emits electromagnetic radiation within a wavelengthregime of interest, for example, visible, infrared or ultravioletregime, when activated, by applying a potential difference across thedevice or passing a current through the device. Examples oflight-emitting elements include solid-state, organic, polymer,phosphor-coated or high-flux LEDs, laser diodes or other similar devicesas would be readily understood. The emitted radiation of an LEE may bevisible, such as red, blue or green, or invisible, such as infrared orultraviolet. An LEE may produce radiation of a continuous ordiscontinuous spread of wavelengths. An LEE may feature a phosphorescentor fluorescent material, also known as a light-conversion material, forconverting a portion of its emissions from one set of wavelengths toanother. In some embodiments, the light from an LEE includes or consistsessentially of a combination of light directly emitted by the LEE andlight emitted by an adjacent or surrounding light-conversion material.An LEE may include multiple LEEs, each emitting essentially the same ordifferent wavelengths. In some embodiments, a LEE is an LED that mayfeature a reflector over all or a portion of its surface upon whichelectrical contacts are positioned. The reflector may also be formedover all or a portion of the contacts themselves. In some embodiments,the contacts are themselves reflective. Herein “reflective” is definedas having a reflectivity greater than 65% for a wavelength of lightemitted by the LEE on which the contacts are disposed. In someembodiments, an LEE may include or consist essentially of an electronicdevice or circuit or a passive device or circuit. In some embodiments,an LEE includes or consists essentially of multiple devices, for examplean LED and a Zener diode for static-electricity protection. In someembodiments, an LEE may include or consist essentially of a packagedLED, i.e., a bare LED die encased or partially encased in a package. Insome embodiments, the packaged LED may also include a light-conversionmaterial. In some embodiments, the light from the LEE may include orconsist essentially of light emitted only by the light-conversionmaterial, while in other embodiments the light from the LEE may includeor consist essentially of a combination of light emitted from an LED andfrom the light-conversion material. In some embodiments, the light fromthe LEE may include or consist essentially of light emitted only by anLED.

One or more non-LEE devices such as Zener diodes, transient voltagesuppressors (TVSs), varistors, etc., may be placed on each light sheetto protect the LEEs 140 from damage that may be caused by high-voltageevents, such as electrostatic discharge (ESD) or lightning strikes. Inone embodiment, conductive trace segments shown in FIG. 1B or 1C betweenthe LEE strings 150 may be used for placement of a single protectiondevice per light sheet, where the device spans the positive and negativepower traces, for example power conductors 120,121. These trace segmentsalso serve to provide a uniform visual pattern of lines in the webdirection, which may be more aesthetically pleasing than a light sheetwith noticeable gaps between LEE strings 150. In a more general sense,in addition to conductive traces 160 that are part of string 150,additional conductive traces 160 that may or may not be electricallycoupled to other strings 150 and/or power conductors 120,121 may beformed on substrate 165, for example to provide additional powerconduction pathways or to achieve a decorative or aesthetically pleasinglook to the pattern on the light sheet or to provide a communicationpathway to one or more CEs 145, for example to provide a control signalto the one or more CEs 145. These trace segments also serve to provide auniform visual pattern of lines in the web direction, which may be moreaesthetically pleasing than a light sheet with noticeable gaps betweenLEE strings 150.

In one embodiment, an LEE 140 includes or consists essentially of a baresemiconductor die, while in other embodiments LEE 140 includes orconsists essentially of a packaged LED.

In some embodiments, an LEE 140 may include or consist essentially of a“white die” that includes an LED that is integrated with alight-conversion material (e.g., a phosphor) before being attached tothe light sheet, as described in U.S. patent application Ser. No.13/748,864, filed Jan. 24, 2013, or U.S. patent application Ser. No.13/949,543, filed Jul. 24, 2013, the entire disclosure of each of whichis incorporated by reference herein.

In some embodiments, LEEs 140 may emit light in a relatively smallwavelength range, for example having a full width at half maximum in therange of about 20 nm to about 200 nm. In some embodiments, all LEEs 140may emit light of the same or substantially the same wavelength, whilein other embodiments different LEEs 140 may emit light of differentwavelengths. In some embodiments, LEEs 140 may emit white light, forexample that is perceived as white light by the eye. In someembodiments, the white light may be visible light with a spectral powerdistribution the chromaticity of which is close to the blackbody locusin the CIE 1931 xy or similar color space. In some embodiments, whitelight has a color temperature in the range of about 2000 K to about10,000 K. The emission wavelength, full width at half maximum (FWHM) ofthe emitted light or radiation or other optical characteristics of LEEs140 may not be all the same and are not a limitation of the presentinvention.

Advantageously, embodiments of the present invention produce a lightsheet 110 having controlled optical characteristics. In some embodimentsof the present invention it is advantageous to have multiple lightsheets, each of which as a similar CCT, preferably the average CCT ofeach light sheet during manufacture or use having a relatively narrowCCT distribution. One measure of white color temperature is defined as aMacAdam ellipse. A MacAdam ellipse represents a region of colors on achromaticity chart, for example the CIE chromaticity diagram, and aone-step MacAdam ellipse represents the range of colors around thecenter of the ellipse that are indistinguishable to the average humaneye, from the color at the center of the ellipse. The contour of aone-step MacAdam ellipse therefore represents barely noticeabledifferences of chromaticity.

Multiple-step MacAdam ellipses may be constructed that encompass largerranges of color around the center point. While there are manyrecommendations as to how tight the color temperature uniformity shouldbe (as measured by MacAdam ellipses or other units), a variationencompassed within a smaller step number of MacAdam ellipses (smallerellipse) is more uniform than one encompassed within a larger stepnumber of MacAdam ellipses (larger ellipse). For example, a four-stepMacAdam ellipse encompasses about a 300 K color temperature variationalong the black body locus, centered at 3200 K, while a two-step MacAdamellipse encompasses about a 150 K color temperature variation along theblack body locus, centered at 3200 K.

In some embodiments of the present invention, the variation in averageCCT between different light sheets 110 is less than 4 MacAdam ellipses,or less than 3 MacAdam ellipses or less than 2 MacAdam ellipses.

Substrate 165 may include or consist essentially of a semicrystalline oramorphous material, e.g., polyethylene naphthalate (PEN), polyethyleneterephthalate (PET), polycarbonate, polyethersulfone, polyester,polyimide, polyethylene, fiberglass, FR4, metal core printed circuitboard, (MCPCB), and/or paper. Substrate 165 may include multiple layers,for example, a semicrystalline or amorphous material, e.g., PEN, PET,polycarbonate, polyethersulfone, polyester, polyimide, polyethylene,and/or paper formed over a second substrate for example comprising,acrylic, aluminum, steel and the like. Depending upon the desiredapplication for which embodiments of the invention are utilized,substrate 165 may be substantially optically transparent, translucent,or opaque. For example, substrate 165 may exhibit a transmittance or areflectivity greater than 70% for optical wavelengths ranging betweenapproximately 400 nm and approximately 700 nm. In some embodimentssubstrate 165 may exhibit a transmittance or a reflectivity of greaterthan 70% for one or more wavelengths emitted by LEEs 140. Substrate 165may also be substantially insulating, and may have an electricalresistivity greater than approximately 100 ohm-cm, greater thanapproximately 1×10⁶ ohm-cm, or even greater than approximately 1×10¹⁰ohm-cm. In some embodiments, substrate 165 may have a thickness in therange of about 10 μm to about 500 μm.

Conductive elements, e.g., power conductors 120, 121 and conductivetraces 160, may be formed via conventional deposition, photolithography,and etching processes, plating processes, lamination, lamination andpatterning, evaporation sputtering or the like or may be formed using avariety of different printing processes. For example, power conductors120, 121 and conductive traces 160 may be formed via screen printing,flexographic printing, ink-jet printing, and/or gravure printing. Powerconductors 120, 121 and conductive traces 160 may include or consistessentially of a conductive material (e.g., an ink or a metal, metalfilm or other conductive materials or the like), which may include oneor more elements such as silver, gold, aluminum, chromium, copper,and/or carbon. Power conductors 120, 121 and conductive traces 160 mayhave a thickness in the range of about 50 nm to about 1000 μm. In someembodiments, the thickness of power conductors 120, 121 and conductivetraces 160 may be determined by the current to be carried thereby. Whilethe thickness of one or more of power conductors 120, 121 and conductivetraces 160 may vary, the thickness is generally substantially uniformalong the length of the trace to simplify processing. However, this isnot a limitation of the present invention, and in other embodiments thethickness and/or material of power conductors 120, 121 and conductivetraces 160 may vary. In some embodiments, all or a portion of powerconductors 120, 121 and conductive traces 160 may be covered orencapsulated. In some embodiments, a layer of material, for exampleinsulating material, may be formed over all or a portion of powerconductors 120, 121 and conductive traces 160. Such a material mayinclude, e.g., a sheet of material such as used for substrate 165, aprinted layer, for example using screen, ink jet, stencil or otherprinting means, a laminated layer, or the like. Such a printed layer mayinclude, for example, an ink, a plastic and oxide, or the like. Thecovering material and/or the method by which it is applied is not alimitation of the present invention.

In some embodiments of the present invention, all or a portion ofsubstrate 165 and/or power conductors 120, 121 and conductive traces 160may be covered by a layer having pre-determined optical properties. Insome embodiments, the optical properties of substrate 165 or a coatingmaterial on substrate 165, for example reflectance, transmittance andabsorption, may be utilized to further control the opticalcharacteristics of the lighting system. In some embodiments, substrate165 or a coating on substrate 165 may be a diffuse reflector, while inother embodiments it may be a specular reflector, and in yet otherembodiments it may be designed to have a relatively high absorbance forlight emitted by LEEs 140. In some embodiments of the present invention,substrate 165 may have a reflectance of at least 80% or at least 90% orat least 95% to a wavelength of light emitted by LEEs 140. In someembodiments of the present invention, substrate 165 may be transparentor substantially transparent to a wavelength of light emitted by LEEs140, for example having a transmittance of at least 80% or at least 90%or at least 95% to a wavelength of light emitted by LEEs 140. In someembodiments of the present invention, substrate 165 may be absorbing orsubstantially absorbing to a wavelength of light emitted by LEEs 140,for example having an absorbance of at least 60% or at least 70% or atleast 80% to a wavelength of light emitted by LEEs 140. In someembodiments, substrate 165 or portions of substrate 165 may beconfigured to diffuse a wavelength of light emitted by LEEs 140. In someembodiments, substrate 165 may have two or more regions, where differentregions have different optical characteristics. In some embodiments, thetransmittance of a diffuse region is at least 50%, or at least 70% or atleast 80%, or at least 90% to a wavelength of light emitted by LEEs 140.The remaining portion of substrate 165 in some embodiments has areflecting surface, i.e., it is reflecting to a wavelength of lightemitted by LEEs 140.

In one embodiment, conductive traces 160 are formed with a gap betweenadjacent conductive traces 160, and LEEs 140 and CEs 145 areelectrically coupled to conductive traces 160 using conductive adhesive,e.g., an isotropically conductive adhesive and/or an ACA, as describedin U.S. Pat. No. 8,384,121, filed on Jun. 29, 2011, the entiredisclosure of which is incorporated herein by reference. ACAs may beutilized with or without stud bumps and embodiments of the presentinvention are not limited by the particular mode of operation of theACA. For example, the ACA may utilize a magnetic field rather thanpressure (e.g., the ZTACH ACA available from SunRay Scientific of Mt.Laurel, N.J., for which a magnetic field is applied during curing inorder to align magnetic conductive particles to form electricallyconductive “columns” in the desired conduction direction). Furthermore,various embodiments utilize one or more other electrically conductiveadhesives, e.g., isotropically conductive adhesives, non-conductiveadhesives, in addition to or instead of one or more ACAs. In otherembodiments, LEEs 140 and CEs 145 may be attached to and/or electricallycoupled to conductive traces 160 by other means, for example solder,reflow solder, wave solder, wire bonding, or the like. The method bywhich LEEs 140 and CEs 145 are attached to conductive traces 160 is nota limitation of the present invention.

CE 145 may be one component or multiple active and/or passivecomponents. In one embodiment, power conductors 120,121 provide a DCvoltage or substantially DC voltage and CE 145 includes or consistsessentially of a resistor, e.g. a current-limiting resistor. The choiceof the resistance value may be a trade-off between a number ofparameters and characteristics that may include, e.g., efficiency andcurrent stability. In general, a larger resistance will result inreduced efficiency but greater current stability, while a smallerresistance will result in increased efficiency but reduced currentstability. Variations in the current may result from variations in theinput voltage (for example across power conductors 120, 121), variationsin forward voltage of the LEEs 140 within the string, variations in thevalue of the current-limiting resistor, variations in current that mayoccur if one or more LEEs 140 in the string become short-circuited orthe like. In the case of CE 145 including or consisting essentially of aresistor, in some embodiments CE 145 is a discrete resistor formedwithin or on conductive traces 160, such as a chip resistor, a bare-dieresistor or surface mount device (SMD) resistor.

As discussed above, in embodiments where CE 145 includes or consistsessentially of a resistor, there may be trade-offs between efficiencyand current stability. While such trade-offs may be acceptable incertain products, other products may require relatively better currentstability at higher efficiencies, and in these cases CE 145 may includeor consist essentially of multiple components or a circuit element, asdiscussed above. In some embodiments CE 145 includes or consistsessentially of a field-effect transistor (FET) and a resistor. Inanother embodiment CE 145 includes or consists essentially of twobipolar junction transistors (BJTs) and two resistors.

In some embodiments, the efficiency and current stability increase withthe number of components, as does the cost. In some embodiments where CE145 includes or consists essentially of multiple components, thecomponents may be in discrete form (i.e., each component individuallyelectrically coupled to conductive traces 160) or in hybrid form (wheremultiple separate components are mounted on a submount, which is thenelectrically coupled to conductive traces 160), or in monolithic form(where multiple components are integrated on a semiconductor chip, forexample a silicon-based or other semiconductor-based integratedcircuit). In some embodiments, CE 145 may be in bare-die form, while inother embodiments CE 145 may be packaged or potted or the like. In someembodiments, CE 145 may include or consist essentially of a bare-dieintegrated circuit. In some embodiments, the integrated circuit includesor consists essentially of multiple active and/or passive devices thatare fabricated on a common semiconductor substrate.

In other embodiments, power conductors 120, 121 may provide AC power, orpower modulated at different frequencies and in these embodiments CEs145 may be selected accordingly or may be omitted. In one embodiment,power conductors 120, 121 may provide a standard line voltage, forexample about 120 VAC or about 240 VAC or about 277 VAC, for example atabout 50 Hz or about 60 Hz. In some embodiments, CEs 145 may accommodatea plurality of input types, and thus be so-called “universal” CEs 145,while in other embodiments different CEs 145 may be required fordifferent input types. The actual component or components of CEs 145 arenot limiting to this invention; however, in preferred embodiments ofthis invention, the positioning of CEs 145 does not disrupt the LEEpitch. In another embodiment of this invention, the positioning of CEs145 is independent of LEE pitch. As discussed herein, CEs 145 and LEEs140 may be electrically coupled to conductive traces 160 using a varietyof means, for example solder, conductive adhesive or anisotropicconductive adhesive (ACA); however, the method of electrical coupling ofCEs 145 and LEEs 140 is not a limitation of the present invention.

In general in the above discussion the arrays of semiconductor dies,light emitting elements, optics, and the like have been shown as squareor rectangular arrays; however this is not a limitation of the presentinvention and in other embodiments these elements may be formed in othertypes of arrays, for example hexagonal, triangular or any arbitraryarray. In some embodiments these elements may be grouped into differenttypes of arrays on a single substrate.

The terms and expressions employed herein are used as terms andexpressions of description and not of limitation, and there is nointention, in the use of such terms and expressions, of excluding anyequivalents of the features shown and described or portions thereof. Inaddition, having described certain embodiments of the invention, it willbe apparent to those of ordinary skill in the art that other embodimentsincorporating the concepts disclosed herein may be used withoutdeparting from the spirit and scope of the invention. Accordingly, thedescribed embodiments are to be considered in all respects as onlyillustrative and not restrictive.

What is claimed is:
 1. A lighting system comprising: a substantiallyplanar flexible substrate having a first surface and a second surfaceopposite the first surface; first and second spaced-apart powerconductors disposed over the substrate; a plurality of light-emittingstrings disposed over the first surface of the substrate, eachlight-emitting string (i) comprising a plurality of interconnectedlight-emitting elements spaced along the light-emitting string, (ii)having a first end electrically coupled to the first power conductor,and (iii) having a second end electrically coupled to the second powerconductor, wherein the power conductors supply power to each of thelight-emitting strings; a plurality of conductive traces disposed overthe first surface of the substrate and each (i) electricallyinterconnecting two light-emitting elements, or (ii) electricallyconnecting a light-emitting element to a power conductor; a plurality ofcontrol elements each (i) electrically connected to at least onelight-emitting string and (ii) configured to utilize power supplied fromthe power conductors to control the current to the at least onelight-emitting string to which it is electrically connected; and apolymeric top housing disposed over the first surface of the substrateand sealed to the first surface of the substrate at a contact pointbetween the top housing and the first surface of the substrate to form asealed region between the top housing and the substrate, the sealedregion containing therewithin the plurality of light-emitting stringsand at least some of the conductive traces, wherein the top housingdefines a plurality of shaped regions each (i) associated with alight-emitting element and (ii) spaced apart from and not in contactwith the light-emitting element with which it is associated.
 2. Thelighting system of claim 1, wherein the sealed region containstherewithin at least a portion of the first power conductor and at leasta portion of the second power conductor.
 3. The lighting system of claim1, wherein at least a portion of the first power conductor and at leasta portion of the second power conductor are disposed over the firstsurface of the substrate.
 4. The lighting system of claim 1, wherein apressure within at least a portion of the sealed region is less thanatmospheric pressure.
 5. The lighting system of claim 1, wherein thelighting system is separable, via a cut spanning the first and secondpower conductors and not crossing a light-emitting string, into twoindividually operable partial lighting systems each comprising (i) oneor more light-emitting strings, (ii) one or more control elements, (iii)portions of the first and second power conductors configured to supplypower to and thereby illuminate the one or more light-emitting stringsof the partial lighting system, and (iv) a sealed region defined by aseal between a portion of the top housing and the substrate.
 6. Thelighting system of claim 1, wherein at least one of the control elementsis disposed within the sealed region.
 7. The lighting system of claim 1,further comprising a plurality of additional conductive traces disposedover the substrate and each (i) electrically connecting a light-emittingelement to a control element, or (ii) electrically connecting a controlelement to the first power conductor or to the second power conductor.8. The lighting system of claim 7, wherein at least some of theadditional conductive traces and at least one of the control elementsare disposed within the sealed region.
 9. The lighting system of claim1, wherein the first and second power conductors are disposed entirelywithin the sealed region.
 10. The lighting system of claim 1, furthercomprising, electrically connected to the first and second powerconductors, a power supply for powering the light-emitting elements. 11.The lighting system of claim 10, wherein the power supply is configuredto provide a substantially constant voltage to the first and secondpower conductors.
 12. The lighting system of claim 1, wherein theplurality of control elements are disposed on the substrate.
 13. Thelighting system of claim 1, wherein at least one of the shaped regionscontains therewithin air, an inert gas, and/or a material that istransparent or substantially transparent to a wavelength of lightemitted by the light-emitting elements.
 14. The lighting system of claim1, wherein at least one of the shaped regions is shaped as a hemisphere,a portion of a sphere, or a paraboloid.
 15. The lighting system of claim1, further comprising a polymeric bottom housing disposed over thesecond surface of the substrate, at least a portion of the bottomhousing contacting the second surface of the substrate to form a secondsealed region disposed between the bottom housing and the second surfaceof the substrate.
 16. The lighting system of claim 1, furthercomprising, extending from within the sealed region to outside of thesealed region, one or more conductive couplings for supplying power froman external power source to the light-emitting strings.
 17. The lightingsystem of claim 16, wherein at least one conductive coupling comprisesan electrical connector terminating outside of the sealed region andconfigured to receive a complementary connector or wire electricallyconnected to the external power source.
 18. The lighting system of claim17, wherein the lighting system has an ingress protection rating of atleast IP 65, as specified by International Protection Marking inInternational Electrotechnical Commission (IEC) standard
 60529. 19. Thelighting system of claim 16, wherein at least one conductive couplingcomprises a conductive element piercing through at least one of the tophousing or the substrate and making electrical contact to at least oneof the first or second power conductors.
 20. The lighting system ofclaim 1, further comprising at least one of (i) control circuitryconfigured to control at least one emission characteristic of thelight-emitting elements, or (ii) communication circuitry configured totransmit information to or from the lighting system.
 21. The lightingsystem of claim 20, wherein (i) the lighting system comprises controlcircuitry configured to control at least one emission characteristic ofthe light-emitting elements, and (ii) the at least one emissioncharacteristic comprises at least one of a correlated color temperature,a color rendering index, R9, a luminous flux, a light output power, aspectral power density, a radiant flux, a light-distribution pattern, oran angular color uniformity.
 22. The lighting system of claim 1, whereineach light-emitting string is electrically coupled to a differentcontrol element.
 23. The lighting system of claim 1, further comprising,extending from within the sealed region to outside of the sealed region,one or more conductive couplings configured to convey a communication orcontrol signal to or from the light sheet.
 24. The lighting system ofclaim 23, wherein the communication or control signal comprises at leastone of a light-intensity level, a correlated color temperature, a colorrendering index, a luminous-intensity distribution, or an operationalstate of the light sheet.
 25. The lighting system of claim 1, whereinthe top housing comprises at least one of polyester, acrylic,polystyrene, polyethylene, polyimide, polyethylene naphthalate,polyethylene terephthalate, polypropylene, polycarbonate, acrylonitrilebutadiene styrene, polyurethane, silicone, or polydimethylsiloxane. 26.The lighting system of claim 1, wherein a weight per area of thelighting system is less than 5 kg/m².
 27. The lighting system of claim1, wherein a thickness of the lighting system is less than 15 mm. 28.The lighting system of claim 1, wherein at least a portion of the tophousing is configured as a diffuser for a wavelength of light emitted bythe light-emitting elements.
 29. The lighting system of claim 1, whereina transmittance of the top housing for a wavelength of light emitted bythe light-emitting elements is greater than 90%.
 30. The lighting systemof claim 1, wherein the light-emitting elements in each of thelight-emitting strings are separated at a substantially constant pitch.31. The lighting system of claim 1, wherein at least one light-emittingelement comprises a light-emitting diode.
 32. The lighting system ofclaim 1, wherein at least one light-emitting element emits substantiallywhite light.
 33. The lighting system of claim 1, further comprising adesiccant disposed in the sealed region.
 34. The lighting system ofclaim 1, wherein at least one of the light-emitting elementsincorporates a light-conversion material for conversion of at least aportion of light emitted by the at least one of the light-emittingelements to light having a different wavelength.
 35. The lighting systemof claim 1, wherein the lighting system is separable, via a cut spanningthe first and second power conductors and not crossing a light-emittingstring, into two individually operable partial lighting systems eachcomprising (i) one or more light-emitting strings, (ii) portions of thefirst and second power conductors configured to supply power to andthereby illuminate the one or more light-emitting strings of the partiallighting system, and (iii) a sealed region defined by a seal between aportion of the top housing and the substrate.
 36. A lighting systemcomprising: a substantially planar flexible substrate having a firstsurface and a second surface opposite the first surface; first andsecond spaced-apart power conductors disposed over the substrate; aplurality of light-emitting strings disposed over the first surface ofthe substrate, each light-emitting string (i) comprising a plurality ofinterconnected light-emitting elements spaced along the light-emittingstring, (ii) having a first end electrically coupled to the first powerconductor, and (iii) having a second end electrically coupled to thesecond power conductor, wherein the power conductors supply power toeach of the light-emitting strings; a plurality of conductive tracesdisposed over the first surface of the substrate and each (i)electrically interconnecting two light-emitting elements, or (ii)electrically connecting a light-emitting element to a power conductor; aplurality of control elements each (i) electrically connected to atleast one light-emitting string and (ii) configured to utilize powersupplied from the power conductors to control the current to the atleast one light-emitting string to which it is electrically connected; apolymeric top housing disposed over the first surface of the substrate;and a polymeric bottom housing disposed over the second surface of thesubstrate and sealed to the top housing at a contact point between thetop housing and the bottom housing to form a sealed region between thetop housing and the bottom housing, the sealed region containing thesubstrate therewithin, wherein the top housing defines a plurality ofshaped regions each (i) associated with a light-emitting element and(ii) spaced apart from and not in contact with the light-emittingelement with which it is associated.
 37. The lighting system of claim36, wherein the lighting system is separable, via a cut spanning thefirst and second power conductors and not crossing a light-emittingstring, into two individually operable partial lighting systems eachcomprising (i) one or more light-emitting strings, (ii) one or morecontrol elements, (iii) portions of the first and second powerconductors configured to supply power to and thereby illuminate the oneor more light-emitting strings of the partial lighting system, and (iv)a sealed region defined by a seal between a portion of the top housingand the substrate.
 38. The lighting system of claim 36, wherein at leastone of the shaped regions contains therewithin air, an inert gas, and/ora material that is transparent or substantially transparent to awavelength of light emitted by the light-emitting elements.
 39. Thelighting system of claim 36, wherein the lighting system is separable,via a cut spanning the first and second power conductors and notcrossing a light-emitting string, into two individually operable partiallighting systems each comprising (i) one or more light-emitting strings,(ii) portions of the first and second power conductors configured tosupply power to and thereby illuminate the one or more light-emittingstrings of the partial lighting system, and (iii) a sealed regiondefined by a seal between a portion of the top housing and thesubstrate.